The Time Traveler's Wife by Audrey Niffenegger
This is a straight-up love story about a man and a woman (Henry and Claire) who just happen to first meet each other at different points in their lives. This is because Henry has a genetic mutation that causes him to time travel. So Claire ends up first meeting Henry when she is about 6 and Henry is time traveling from his mid-30s. Henry first meets Claire when she chances to visit the library that he works at, while he's not time traveling. Are you confused yet? The rest of the story describes how Henry and Claire attempt to maintain their relationship through not only the uncertainties of regular life but the added complications of Henry's time traveling, which happens involuntarily and with little advance warning.
If you are easily confused by time travel and causality paradoxes then you probably shouldn't read this book. Although the author provides useful dates, ages of the leading characters in the current scene, and indicates which narrator is speaking it might be easier to follow along if you create your own timeline of the two characters' lives.
The reason I call this science fiction without the science is because there is no science. Well, okay, maybe a tiny, minuscule, vague hint at science in one chapter when Henry visits the geneticist. That's it. Henry's time travel has nothing to do with levers, gears, complex chemical reactions, etc. It just happens. The only common denominator is Henry's stress level, which is consistently very high, especially for someone who works in a library. Maybe if he didn't time travel so much he'd have less stress...but wait, that's what causes him to time travel...oh noes!
So yeah, there's a few paradoxes that crop up because Henry invariably visits times and places and people that he knows in the past or will know in the future. Henry states that actions in the past or the future have already happened bringing up loads of questions about free will. In my mind it doesn't necessarily negate free will, people remain free to choose their actions, Henry just happens to already know their choice. The paradox then comes when he shares his future knowledge with people. You're left with a situation where that person made a particular choice because of what Henry told them but what Henry told them was based on the fact that they had already made that particular choice. Okay, now you're confused.
In summary, Niffenegger wrote about 150 more pages than was really necessary. She wrote excellent foreshadowing but because of Henry's statement of causality early on, the last part of the book becomes fairly predictable. I wouldn't classify this as science fiction as other people have but nevertheless it is a pretty good story.