Oh boy, where to begin….
STAR TREK
“Hard Rain” doesn’t really do enough with the concept and is, over all, un-satisfying. Below are generally considered to be the best…
TOS
Yesterday’s Son (A.C. Crispin) The 1st Trek book to be a NY Times best-seller. Spock had a son with Zarabeth (“All Our Yesterdays”). He has to rescue him from the past.
The Vulcan Academy Murders (Jean Lorrah) Great mystery set at the Vulcan Science Academy.
Strangers From the Sky (Margaret Wander Bonanno). Tells the story of the first contact between Earth and Vulcan. Later, completely invalidated by the move “First Contact” but a lot of fun.
How Much for Just the Planet? (John Ford) The only TOS comedy novel. Takes place on a planet where people burst into a song a lot (STAR TREK: THE MUSICAL)
Time For Yesterday (A.C. Crispin) Sequel to Yesterday’s Son. Just as good.
Spock’s World (Diane Duane). First TOS hardcover. Is Vulcan going to withdraw from the Federation? Political machinations and history collide.
Vulcan’s Glory (D.C. Fontana) Another great mystery set aboard the Enterprise, by the woman who wrote a lot of the Vulcan-centered episodes.
Federation (Judith & Garfield Reeves-Stevens) Recently voted “Favorite Trek Novel” by a Trek BBS, Kirk, Picard, and the inventor of warp drive, Zephram Cochran (again, written before “First Contact” so different from the one we see in the film), don’t exactly meet, but their destinies collide. Full of history and cross-references between shows. It’s one of my favorites.
Sarek (A.C. Crispin). Tells three separate stories, all intersecting. If you like Sarek, and you like Vulcan, this is a must.
Prime Directive (Judith & Garfield Reeves-Stevens) After Kirk appears to have destroyed a planet, the crew is disbanded and go their own ways. But then they rejoin to prove his innocence. I’m not doing it justice. It’s a good read.
The Return (William Shatner, Judith & Garfield Reeves-Stevens). There are also a lot of books by Shatner (and Judith & Garfield Reeves-Stevens). These take place in a universe where Kirk was brought back to life after “Generations.” This is the best of them. Kirk and Picard interacting in a meaningful way to fight the Borg and the Romulans.
Assigment Eternity (Greg Cox). If you liked Gary Seven and Roberta Lincoln (Teri Garr), you’ll love this. Chocked full of amusing 60s references and references to other TV spy shows. FUN!
TNG
Q-in-Law (Peter David). Like Q? Like Lwaxana Troi? Very amusing novel. Peter David is one of the best of the Trek novelists.
Reunion (Michael Jan Friedman) Someone is killing Picard’s old crewmates from his days commanding the Stargazer as they attend a reunion. The most emotionally-packed and best-written of all Trek novels. If you like Picard and Crusher, this is the novel for you. The only Trek novel ever to make me cry.
Dark Mirror (Diane Duane) Picard and Co. must fight their evil twins in the Mirror Universe. Written before the folks in DS9 started going over there every other week, but of you dig “Mirror, Mirror,” this is for you.
Imzadi (Peter David) The story of Riker and Troi’s relationship along with a dash of time travel. Very nice. Consistently a fan favorite.
Q-Squared (Peter David). Remember Trelane, (“the Squire of Gothos”)? He was just a Q in training. He, Q, and others bedevil Picard. Great in that it has three alternate time lines (usual TNG, a TNG with Jack Crusher alive, and the “Yesterday’s Enterprise”) colliding head on.
Rogue Saucer (John Vornholt) A prototype “just-saucer” starship is stolen by terrorists. Great adventure.
Diplomatic Implausibility (Keith R.A. DeCandido). Worf’s first job as an ambassador, following the end of DS9. Like Worf? This is for you.
DS9
Anything published in the year 2000 or after is great! If you are into alternate time lines, the “Millennium” trilogy by Judith & Garfield Reeves-Stevens rocks! Then there are the “Avatar” books by S.D. Perry, which are the “re-launch” of the series after the last episode. The books being written now that the show is off the air are better than those while the show was on.