I've just ran across this thread, and I'd like to share my opinions on the books (aside from Captain's Peril. I skipped it
The Ashes of Eden: A fairly good TOS novel set after TUC. It's a fun read with some good development of character and action. Shatner's ego was, er, pretty well in check...
The Return: Not the best Trek novel by any means, and it has more action than even Die Hard (which isn't so bad, really..), but it also makes for a fun story of Kirk's resurection and the TNG crew fighting the Borg...oh, and the USS Monitor is a neat device. But the best part of the book was the Borg subplot
Avenger: An interesting story involving Kirks re-return and a little twist on Ambassador Sarek's death.
Spectre/Dark Victory/Preserver:The first is awesome, IMO. The little trick with the USS Voyager was clever. 2nd was kinda eh, but with lots of mystery. Third...wellllll....it was neat, but not SUPER awesome. (As some others have said, it is rather cartoonish.
Captain's Blood and Glory were pretty dull for the most part.