With a setup that recalls Groundhog Day and Back to the Future II (a middle-aged man, Jeff, relives his life from age 18 to his "death" at 43 over and over, able to change things each time but never escaping the loop; going back in time gives him a chance to make a fortune betting on horse races), Replay promises to be a fun sci-fi wish fulfillment story, but winds up something else entirely, a wistful meditation on the relentless passage of time and the regrets we all carry about the choices we didn't make and the risks we didn't take.Don't go into this looking for a hard SF exploration of how or why Jeff is time traveling, because that isn't this book. Most of it is actually a love story that develops over more than a century's worth of years when Jeff happens upon another caught in the same loop and the two try to make sense of what is happening to them, building and rebuilding a life together, retaining all of their memories each time they complete a cycle (Jeff calls them "replays") and loop back. Some of these variations are pretty dark (Jeff nihilistically descends into drugs and sex), but others are fun (Jeff and the love interest change the world by creating an ecologically-themed Star Wars type movie years before Star Wars in an effort to inspire others to live better, a section that is full of cool details for movie buffs). Of course, things get more complicated as the replays become shorter and shorter, each time beginning a few months or years closer to Jeff's unavoidable date of death, which never changes. Some of the replays are far from happy, and Jeff realizes that even with several lifetimes to live, there's never enough time to avoid regrets. In the end, living is about recognizing that, and always moving forward.Wikipedia says Grimwood was working on a sequel when he died (rather young) in 2003. It's hard to imagine where he would have gone with the story, which is wrapped up pretty well, but I'm sorry it won't continue.