Just completed "Available Light" I rated it above average overall.
I found myself much more fascinated with the Section 31 elements of the story and the fallout of the revelations in the novel "Control". We do learn the final fate of Admiral Ross, first of all, and we hear a bit about some characters who we haven't seen in a while like Admiral Nechayev and Admiral Jellico. We also learn of the Klingon reaction to the revelations of what happened at Tezwa and President Zife's role in it all. Much of that is unresolved probably because I expect David Mack to continue that story line in force in his next novel. So "Available Light" probably serves as a bridge of sorts in that respect.
However, that is not the primary story. The Enterprise finds what they believe is a derelict in space, a very large derelict. And while investigating they are attacked by ships looking to scavenge what they think is a derelict and they believe the Enterprise is there to steal the booty from them. Eventually they find the derelict is not so abandoned as they thought, but is inhabited by a race who has basically reduced themselves to a virtual consciousness maintained by the ships computer. Comparisons are made to what Scotty did in "Relics" with the transporter.
Another similarity I was surprised wasn't mentioned is to what was done in "The Thaw". The aliens there did much the same thing to preserve their consciousness and the computer created a virtual environment for them to keep their minds active, like the novel. Now their bodies were not reduced to 'date storage' like they were in the novel, but the consciousness end of things seemed similar (except in the case of "The Thaw" the computer manifested their fears as the 'clown', whereas in the novel their computer technology was much more sophisticated). Still I was a bit surprised when they were considering prior similar circumstances no mention was made of that experience by Voyager. But I digress.
Eventually the inhabitants solicit the Enterprise's help through Chen, and while trying to help them they have to defend against the scavengers. They learn the ships builders had to leave their homeworld secondary to the end stages of pollution and a greenhouse effect that made their home uninhabitable, basically.
I was personally very drawn to the Section 31 fallout elements of the story. But that's a secondary story here. The primary story has to do with the space vessel. That part was pretty good mostly, though somewhere in the middle of the novel my attention started to waver a bit, but it picked up again as we got closer to the end.