Decent Star Trek story, although the time travel aspect is a bit overdone. Overall it's well told, although the plot moves slowly and there isn't a lot of action, even during sequences that could support it. A few of the characters suffer from poor dialog, which keeps them from sounding much like their actual TV selves. I enjoyed reading it once, but wouldn't bother keeping it to read a second time.
This is a fantastic Star Trek book. First of all, it focuses on Scotty and there are not enough Scotty books out there. Second, it skirts over and references several of the movies and TV shows. From Scotty's appearance on Next Generation to the events in Star Trek III, Star Trek IV and Star Trek Generations. The plot itself hinges on Kirk's death in Generations.
The story is basically this: Scotty is depressed after losing Kirk. He hitches a ride on an ill fated ship that crashes into a Dyson Sphere and leaves him trapped in a transporter buffer until Riker releases him 80 years later. Lost and wandering, Scotty happens upon an abandoned Klingon Bird of Prey and decides to recreate the slingshot maneuver from Star Trek IV and travel back to rescue is best friend and commander, Kirk. Picard tries to stop him, gets pulled back in time also and they discover that the Borg have somehow assimilated almost the entire galaxy erasing the existence of the Federation. They must figure out what went wrong and put everything back the way it was before they can return to their normal timeline.
There's time travel, the Borg, alternate realities; everything you could possibly want in a Star Trek novel. It's lots of fun. If you enjoy reading Star Trek novels, this is one of the great ones.