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.
Heaps of great ones here, and some I need to add to my list.
I’ll add a couple that come close to being time travel, but I guess are more like time dilation stories -
Tau Zero by Poul Anderson, about a group of colonists on a ship that is accelerating towards the speed of light, only for a catastrophic failure to cause the ship to become unable to decelerate - leaving them to accelerate forever into space.
The Inverted World By Christopher Priest - A dystopian world stretches out in all directions, and in it a massive, decaying city on rails creeps forwards. Time accelerates out into the past behind it, causing increased passage of time and age for anyone back there - but the future stretches out in front, slowing down time for anyone who moves too far ahead. Everything must move at walking pace, and tracks pulled up behind the city before they rust and buckle, to be laid in front so that the city can keep moving forward, into the present.