My beef was with your suggestion that, somehow, Greg Cox was not a “serious” answer. Seemed insulting to someone I consider quite serious.
But then you also list M&C as favorites, and I consider their books among the worst Star Trek titles ever published, so clearly mileage varies…
Yeah, I'm afraid when I think of M&C I think of the worse books ever written in Star Trek history, particularly the
Phoenix novels. I got to the point with
Fate of the Phoenix I didn't even care how it was going to end. But as in all things individual tastes vary.
And Greg Cox is one of my favorite authors as well. To this day I continue to recommend his 3rd Khan novel,
To Reign in Hell to any fan of TWOK. One of my all time favorites. I loved how he reconciled things between "Space Seed" and TWOK, including some things I didn't even realize, LOL. And of course his
Foul Deeds Will Rise took place between TFF and TUC, a period of time that few novels touch on surprisingly. I hope maybe Christopher will continue his
Ex Machina continuity novels and maybe move past TFF at some point as well.
One novel I always throw out there whenever one of these questions comes up is
Chain of Attack by the late Gene DeWeese. It doesn't often come up in others 'best of' lists but it was the first novel I read that I absolutely loved. I read it over a weekend, which is rare for me. It usually takes me about 3 to 4 weeks to read a MMPB novel. I loved that they get flung in a far off galaxy (so no Starfleet makes sense), and it has an ominous and foreboding tone to start, and Kirk has to play the part of a diplomat in addition to being a soldier. Really Kirk at his best.
Also, while I've not always been a huge fan of Diane Carey's novels (they're ok, but her books are sometimes hard to follow), but I actually did like her
Dreadnought and
Battlestations! The latter is actually the first original Star Trek novel I ever read. I was just getting into Star Trek at the time. Carey actually did a pretty good job of creating an original protagonist with Lt. Piper while avoiding any Mary Sue issues. I never felt Kirk, Spock and co. were lessened to make Piper look better for instance. They are still important and key characters to the story.
Dreadnought should be read first though because
Battlestations! is actually a sequel (I didn't realize that at the time).
Another I'd highly recommend is the novelization for
Star Trek V: The Final Frontier by JM Dillard. Perhaps unusual since the movie isn't the highest rated film in the franchise. But she does lift the story up. It's still not perfect, I mean, she is limited by the movie script itself. But she brings it up as much as possible and addresses some weaknesses in the movie.
I also always liked another novel by Gene DeWeese,
Engines of Destiny. I know some don't like this novel as much but I've always been fascinated by stories about if you can change history, would you? What kinds of unforeseen consequences would there be. In this story Scotty goes back in time from the 24th century after his 'resurrection' to save Kirk from the
Enterprise-B. He thinks he addressed everything because he makes sure he rescues him just after he saves the ship but in a split second before the hull is ruptured leading to 'his death'. But then he is obviously not there for Picard in the Nexus in Generations, and that also has affects on First Contact.
If you like "The City on the Edge of Forever" I'd recommend DRGIII's
Crucible trilogy. It centers of McCoy, Spock and Kirk (one for each novel) and it focuses on the consequences of what happened in the episode. Especially interesting is in the McCoy novel, we get a glimpse of the 'changed' history when McCoy rescues Edith Keeler. He lives a whole life in that altered timeline and McCoy slowly starts to realize things have changed significantly as WWII stretches into the 1950s.