Replay by Ken Grimwood.

A man dies in 1988 and wakes back up as himself in the 60s, but with current memories.

I think people can probably take different things from this book, but one thing I got out of it was an appreciation for the fact that I very likely wouldn't have any of the things I treasure in life, had some of my tragedies not adjusted my course.

Even if you could go back and "do things right", you're a different person with all your future experiences. What if in trying to fix the past, you lost something you couldn't live without?