Audrey Niffenegger's The Time Traveler's Wife can be found in two places on Amazon's virtual bookshelves: Women's Fiction and Science Fiction. Few books have such a claim to fame. However, the novel successfully straddles the line between two genes. A scientific concept--time travel based on flawed DNA--is central to the book. On the other hand, the novel is really about a romantic relationship--beginning, middle and end.
Despite its "women's fiction" label (a genre I usually don't enjoy), I must admit I loved this book. It was filled with incredibly poignant moments and realistic characters I grew to love. It suffered from a little bit of a sagging middle, but the rest of the book more than made up for that. Apparently, the book has been made into a "major motion picture" which will be coming out in August. I encourage you to read it before you see the Hollywood version.