This was not a bad book, but the rave reviews are largely unearned. I think most of the hype over this book was from non-sci-fi fans who liked it as a romance novel and thought the time travel made it even more interesting. The romance was fine, but that's basically all it is: a romance that aspires to be a literary novel, with time travel added as a plot device that lets the main character meet his wife repeatedly throughout her life in a non-linear fashion.
The time travel is never really explained, because it's not the point, so don't expect much discussion of paradox, causality, and all the other issues you'd expect a science fiction novel dealing with time travel to address. In the end, it's a charming little book with a neat plot device, but I really didn't think it was anything special. I should also note that I found the protagonist, the time traveler Henry, to be a rather unsympathetic, unlikeable character.