Demons is not your standard Star Trek novel - it definitely has an element of darkness in it that pervades the plot and insinuates itself into the characters as well. Written as a prequel to the TNG book Posession, it starts in the farthest reaches of the galaxy where an ancient evil force (seems like I have heard of this one before) reappears, overwhelms the Vulcan explorers and heads toward the Sol system.
Intent on taking over the planet Vulcan, our intrepid heros must find a way to stop the evil insanity (I feel like I sound like a tv commercial here) and save Vulcan. If this dark force succeeds, Vulcan will be plunged into an emotional madness that is even worse than the one that almost destroyed their entire civilazation before the times of Surak.
Dillard writes well, especially when exploring the original series. I especially liked the inclusion of Spock's mother, Amanda although she was a bit wishy washy - not at all like the strong and opinionated wife of the Vulcan Ambassador. We also have the usual banter and bickering between Spock and McCoy, althoug it is not quite as entertaining this time, probably given the circumstances.
All in all, the book is 20 years old, it is centered on Vulcan, not exactly a party planet, so while not an amusing read, it is still a good one given the plot and storyline. If you are interested in following along the cast and characters thru the books in order, # 30 is a realtively easy read and should beincluded in the stack.