Right then. Time travel, one of my favorites.
If you don't mind a gay protagonist, the Do Over series by Dan Kirk is quite good. (
link to his stories) The character(s) go back in time, each story is a different iteration. The series explore the combination of the butterfly effect and time travel quite well. Additionally, despite every story being an iteration of the same, you hardly have the feeling that you're reading the same story.
L Sprague De Camp wrote a time-travel story as well entitled
Lest Darkness Fall.