Star Trek Department Of Temporal Investigations Forgotten History
This series is definitely written with the "continuity obsessed" person in mind, as it makes reference to previous novels and all the various Star Trek series, from the original to the animated to Star Trek: Enterprise. The main story takes place the year after the incident with V'ger. Spock had taken a leave of absence, to sort out his feelings and situation. Sulu is thinking about a Captaincy in the future. The main story is that Miri's planet has disappeared. Remember, that's the planet they visited during the original five year mission where all the adults had died because of a plague--and the slowly aging children are hundreds of years old. It's explained that that planet was a duplicate of Earth from another time-line-- and when the Enterprise goes to investigate they get pulled to that alternate Universe, where the Federation doesn't exist. In fact, the Vulcan's are more warlike and have their own Empire. Without contact with humans the lost teachings of Surak were never recovered by Jonathan Archer. While this is happening a Vulcan war ship gets transported to our universe and there's a surprise. On board is the alternate universe version of T'Pring, who Spock was betrothed to. However, the least interesting story involve the DTI itself, as it's pretty much one note, and Lucsly and Dulmur are dull.
If you enjoy Star Trek books you'll like this, as it's a quick read.