1) Burning Dreams by Bannono it takes place after Pike is left on Talos IV and its essentially what happens after and his biography. Spock also visits.
2) Vendetta by Peter David. Its about the Borg but also connects with the Star Trek episode about the Doomsday Machine. The one that looks like a carrot.
3) First Frontier by Diane Duane. Dinosaurs and Star Trek. Shows what would happen if dinosaurs never were wiped out.
4) How Much For This Planet by ? Comedy and Star Trek.
Avoid ALL by Marshak and Culbreath who cowrote at least 4 novels. They also were the earliest fan fic writers and may have created slash Kirk/Spock but not certain. Very masochistic novels. Kirk is almost always near death or close to it. I just read their published novels.