I loved the mirror universe trilogy, I've re-read it a bunch of times. All the stuff with the conspiracies and mysterious happenings was great. I also like how the books tend to have Kirk and Picard sort of at odds with each other; it's more interesting than having them Team Up To Save The Galaxy. All the books are over-the-top fun, and the only one I didn't really like was the 2nd Totality book, with Kirk and an ancient McCoy running around on Remus. A bit much, I think.