Well, in the novels, things have, as usual, gotten complicated. SPOILERS FOR EVERY DAMN NOVEL I KNOW OF SET AFTER DS9'S END AHEAD
Almost as soon as the war ended, Chancellor Martok and Ambassador Worf seek to return to Qo'noS. Unfortunately for them, a Klingon named Morjod launches a major coup d'etat at this point, destroying the Great Hall, killing almost the entire High Council, and declaring Martok a traitor and Federation puppet. Martok is eventually able to take back the empire and kill Morjod, but it nontheless exposing the major rifts still existing in Klingon society over the source of Martok's claim to power and his status as a commoner. Over the next four years, the Klingons start expanding again, conquoring several races on the other side of the Empire away from the Federation and rebuilding the Klingon Defense Force much quicker than Sloan seems to have assumed they'd be able to.
In the immediate year after the war, the Federation faced a number of major crises. First off, the war almost reignited when a rogue Jem'Hadar starship attacked DS9. Soon after, another major crisis occured when the ancient Iconian Gateways were reopened all across the galaxy by a species that was impersonating the thought-to-be-extinct Iconians and were trying to sell the Gateway system to the highest bidder, causing ships to end up in all sorts of places when they'd fly into one of the space-borne gateways. Starfleet eventually shut that down, but it certainly screwed a lot of folks over. Around that same time, several sectors of space were severely damaged by the Genesis Wave, which was a weaponized version of the Genesis Device that destroyed a number of planets. There was also a crisis involving warp drive or some such, but I missed those books and can't tell ya much about 'em.
Anywhos. Bajor joined the Federation in late 2376, but just as they were about to sign the documents inducting them in at the ceremony on DS9, First Minister Shakaar Edon was assassinated by a Trill. Turns out that Shakaar had been infested by one of the Parasites from TNG's "Conspiracy," and that these Parasites were intending to use Bajor as their new staging ground for taking over the Federation. Also, it turns out that the Parasites are actually a mutated offshoot of the Trill Symbionts, a fact that the Trill government had been keeping secret from the rest of the Federation. The Parasite crisis on Bajor was thwarted, but the revelation of the Parasites' true origin and of the subterfuge ignited pre-existing social unrest on Trill about the unofficial and unacknowledged discrimination faced by Unjoined Trills. This culminated in a major terrorist attack by an extremist Unjoined faction that used an EM weapon to kill the majority of Trill Symbionts -- something like 60 to seventy percent, IIRC, were killed, including most of the Trill government. The President of Trill then ordered all new joinings to be cancelled and that all surviving Symbionts be returned to the Symbiont Pools to replenish their numbers, effectively ending the practice of joining for decades to come.
Meanwhile, word finally got out that the Andorian species, due to its unique four-sexed reproductive system, was facing a major genetic crisis and was expected to go extinct within two hundred years unless a way could be found to increase Andorian fertility, a task made excedingly difficult because of the four-sex paradigm and because of conservative Andorian cultural notions about reproduction.
On Cardassia, a civilian government, a democracy led by Alon Ghemor, nephew of Tekeny, had taken hold, but was facing stiff opposition from former Central Command hardliners. On top of that, Cardassia is still in ruins and rebuilding, dependent upon Federation aide (which Bajor is the major staging ground for), and combating major diseases that were killing thousands.
Over in the Gamma Quadrant, the Dominion's Great Link was resisting the changes suggested to it by Odo... until Odo discovered that the true reason that the Hundred were sent out was to attempt to lure the Progenitor, an entity that the Founders regard as being their god and creator, back to the Founder Homeworld. It worked -- but it also turns out that the Progenitor died upon being exposed to radiation from a star going supernova near the Homeworld. The Founders, in mourning because their actions caused their god's death and because they are unable to reproduce themselves, disbanded the Great Link, leaving the Dominion... and leaving Odo and Laas as the last two Founders in charge of their empire.
Meanwhile, an ancient race whose name I can't recall from the Gamma Quadrant was rescued from an alternate dimension. This race also worships the Prophets/Wormhole Aliens... and their reemergence caused the Bajoran Wormhole's Gamma Quadrant terminus to move, opening in the Idran system. Their emergence has also coincided with the arrival of a new Gamma Qaudrant threat known as the Ascendents, but little else is known about them.
And that's all just in 2376.
In early 2377, a new species known as the Watreii attacked and destroyed a Romulan colony. Possessing very powerful technology, and facing an unstable economy because of the economic excesses of former Praetor Dralath (who was in charge in the 2330s, 40s, and 50s, and was responsible for things like the Khitomer Massacre and the Narendra III attack), Praetor Neral ordered the Imperial Fleet home to Romulus to face the incoming Watreii, who were planning on wiping out all Romulan life on Romulus, claiming it to have originally been their world. The Federation and Klingon Empire refused to get involved, but a small fleet of civilian ships and Starfleet ships gone rogue is known to have entered Romulan space to try to help the Romulans. During their first encounter with the Watreii, Pavel Chekov, who was in the fleet, died. (The next two books about the Watreii/Romulan affair haven't been released yet, but what we can infer is that the Watreii affair will likely end with Hiren becoming Praetor, the rise of Shinzon to prominence, and the Federation/Romulan alliance ending, setting the stage for NEM.)
Later that year, it's discovered that a Federation Member State's race, the Selelvians, have been using mind control powers to manipulate the Federation Council. The Federation kicks Selelvia out, and it allies itself with the Tholian Assembly and the Orions, launching a brief war with the Federation. Naturally, the Feds win, but things are simply not lookin' good lately.
Jumping ahead on the chronology to the next year we have info for:
In early 2378, many of the sentient holoprograms that had become common in Federation society, inspired by the Doctor's holographic rights movement, launch what comes to be known as the HoloStrike, bringing interstellar commerce and travel to a hault. I haven't read the books that feature the conclusion to the HoloStrike, so I can't tell ya much more. Also, Federation President Min Zife of Bolarus comes under criticism for signing off on the unconstitutional detentions of former Borg Voyager crew members after Borg technology is found on Earth that begins transforming people into drones via airborne nanoprobes before Janeway and Co. are able to end the threat.
In late 2378, an incident at a war battle site results in the accidental destruction of the USS Juno and an Ontailian ship at the hands of the USS Enterprise. Ontail is a Federation Member, and they're about ready to leave the Federation over it before Picard agrees to allow the blame to be laid unjustly at his feet, tarnishing his reputation. The situation is further complicated by an economic crisis brewing in the UFP, as Member States that had not been damaged by the war start resenting having to continue to contribute resources to help rebuild Members that had been devestated by the war, so much so that a minor secessionist crisis brews. It doesn't lead to war or anything, but it's a problem nontheless.
In mid-2379, a Federation Member State called Delta Sigma IV is rocked by civil war when the two species that had settled it ages ago start fighting. Starfleet eventually figures out that the problem's caused by chemicals in the atmo and finds a temporary solution to stop the violence.
In late 2379, a deal Zife made way back in 2373 when he first took office comes back to haunt him. Zife had signed off on a plan from his Chief of Staff, Koll Azernal, to have the independent world of Tezwa armed with massive, planet-bound nadion pulse cannons that had been developed for use against the Borg. The initial plan was that, if the Dominion War went poorly, the Federation would lure the Dominion fleet to Tezwa, where the cannons would annhilate them. Unfortunately, arming this world was a violation of the Khitomer Accords, as Tezwa was on the Klingon border, and so it was done in secret, without even Starfleet knowing about it, through the Orion Syndicate. Unfortunately, the Tezwan Prime Minister, Kinchawn, was a nationalist fanatic who militarized his economy and purchased a small fleet of Danteri warships, intending to threaten a Klingon colony and use the cannons to fight the Klingons if they tried to retaliate. The Federation tried to intervene, and sent the Enterprise with a fleet of Klingon ships to negotiate a settlement; instead, Kinchawn ordered the arrest of the Starfleet and Klingon delegations. The Klingons retaliated by firing on the surface, devestating the planet, and then the entire fleet save the Enterprise was destroyed by the cannons.
The Klingons prepared to launch an invasion force, but Zife knew that if they found out where the cannons came from, they would declare war on the Federation within days. Zife ordered Picard and Co. to destroy the cannons and prevent the Klingon invasion, still concealing their true origin from them. Our Heroes managed to get access to the Klingon computer override codes with help from Worf, disabling the Klingon fleet remotely and taking over the cannons via commando tactics. This prompted Kinchawn's enemies to launch a coup; in order to keep the Klingons from pursuing the matter further, though, Picard was forced to claim an old Klingon right that made Tezwa a conquest of the Federation.
The Federation then had to occupy and rebuild Tezwa, but faced an insurgency from Kinchawn and his loyalists, losing thousands of personnel. Eventually, Starfleet uncovered evidence of where the cannons had come from. Picard made a deal with Admirals Ross, Nechayev, Paris, Jellico, and Nakamura to force President Zife, Azernal, and Secretary of Military Intelligence Nelina Quafina from office, essentially at gunpoint, because they knew that they couldn't let Zife and Co. get away with what they'd done but also couldn't expose them without prompting a war with the Klingons that would end in the Federation and Klingon Empire's mutual destruction. Picard and the admirals had all thought that Zife and Co. would be out of office and put into protective custody, but unbeknownst to them, Section 31 forced Admiral Ross to allow them to assassinate Zife, Azernal, and Quafina.
As far as the galaxy knows, though, President Zife resigned three years into his second four year term of office and before his next election (Federation Presidents don't have term limits), and within days of the eventual Federation withdrawl from Tezwa, because, he claimed in his speech, new leadership was needed for the post-war era. His resignation prompted what was only the second special election in Federation history, and within one month, a new president was in office -- Nanietta Bacco, former governor of Cestus III. Her only competitor had been a guy named Arafel Pagro, a Federation Special Emissary from Ktar, who had had a hawkish foreign policy stance, arguing that the Federation couldn't continue to be allied with the Klingon Empire when it went around conquoring people. Bacco, who favored continuing the alliance, thankfully won.
Almost as soon as Bacco came to office, Shinzon's coup happened and the events of NEM transpired.
So, it's now 2380. In the wake of NEM, the USS Titan was sent to Romulus to help work things out. Sentator Tal'Aura, the senator who conspired with Shinzon to kill the Senate, had installed herself as Praetor, but her rule was contested by several different factions, from a hawkish pro-war and anti-Federation faction led by former Senator Pardeck, to the Tal Shiar (led by a new chairman who had recently assassinated Koval, the Section 31 mole), Spock's Unificationist group, a significant segment of the Romulan Imperial Fleet led by Commanders Donatra and Suran, and the Remans. Riker's job as captain of the Titan was to facilitate talks with all of the factions to work out a power arrangement and to provide emergency relief services to the Romulan people, whose supply lines were being damaged in the wake of the government's fall. The Remans had managed to build up a large fleet of old ships, but the Imperial Fleet, weakened by political disunity stemming from the Senate's fall, contested command within the fleet, and by the Watreii affair, was barely able to assemble itself to defend Romulus. Eventualy, Riker worked out a cease fire whereby the Remans would become the protectorates of the Klingon Empire, which would maintain a fleet within Romulan space to protect the Remans and allow the settlement of a soutehrn continent on Romulus by the Remans.
This arrangement ended up not working out too well. While Tal'Aura was eventually able to win the support of most of the Romulan factions, much of the Imperial Fleet was barely under her control, and numerous firefights were breaking out between Romulan and Klingon ships, while there was constant violence on Romulus between the Romulans and Remans. Eventually, the Bacco Administration proposed that the Remans be resettled to a planet within the Klingon Empire, and they consented. The deal was done. However, in late 2380, Donatra's fleet assembled at a number of important Romulan farming worlds and declared independence; they were now, they said, the Imperial Romulan State, and Donatra was its empress.
And that's the state of the galaxy as of the end of 2380.
