Once the action starts, the plot is pretty fun. But this is over a third of the way through. Until then is exposition about the physics of the time travel. This was written in the late '90s, when everything mysterious had 'quantum' in the title. Although the physics explained seems correct, it really has no use toward the story. He should've just left it mysterious.

And, with a little bit of clunky prose as well, I can't recommend this book.