Sarek and Amanda - Sarek McCoy - The Crucible: Provenance of Shadows (not a fan of the premise behind McCoy's behaviour, but a good story) Young Spock - Vulcan's glory Middle aged Spock - The Crucible: The Fire and the rose (aka Spock has a midlife crisis) Retired Scotty - Engines of destiny Ezri Dax - Worlds of Star Trek No.2 The Trill
The Captain's Daughter is an excellent book for Sulu. While echoing Crucible for both Spock and McCoy, I'll add The Covenant of the Crown for McCoy and Ex Machina for Spock. The Entropy Effect is a great Kirk and a great Spock book, but it utterly fails with both Scotty and Sulu. Oh, and both Yesterday... novels for Spock, as well.