My pick would have to be the A Whole Nother Story trilogy, in which (spoiler warning) you can only travel back in time. But because time is in a loop of sorts, if you go before the beginning of time, you will be at the end of time. From there you can go back to any time you want to. And time paradoxes cannot be produced. Plus, your memories from the previous timeline exist as well as the memories from the new one.
Pastwatch: The Redemption of Christopher Columbus by Orson Scott Card. Starts off with people of a future dying earth being able to see into the past, until they discover they may be able to physically go back and change it