The First Fifteen Lives of Harry August

I'm a sucker for stories where the main characters is stuck in a time loop. Groundhog Day and Edge of Tomorrow stand out, but this one took it to an entirely new level. The title itself is a giveaway for the time loop – an entire lifetime. The concept of replaying your entire life sounds interesting, but the complications that come up when you (and perhaps others) can do this were problems I hadn't seen explored in Sci-Fi before.