Wow! It's really hard to pick a favorite I also Like Doctor's Orders by Diane Duane and the Crucible Novel about McCoy is also really good.I really like A choice of Catastrophies & Dreams of the ravens. Also there's another McCoy novel about McCoy and his daughter Joanna Crisis on Centaurus.by Brad Ferguson
I picked Ravens. I really enjoyed that book. I've read it a couple of times.
But I haven't read the others though.
I'm put off "Doctor's Orders" by one review that said that Spock should have taken over at the first sign of trouble. I can't get over that.
I hate the Crucible series. The McCoy novel was the best though IMO.