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.
I feel like it’s important to mention that she’s a modern Black woman pulled back to a plantation in the 1800s where her ancestor is enslaved. It’s phenomenal but very very heavy.
There’s a great interview with Octavia Butler floating around where she’s asked about the themes of race and identity in her books. She sort of brushes it off is just another tool to write about lol.
One of her strengths is to handle this material in such an objective way. She’s a black female author presenting her ideas in the most masculine way. She really is one of a kind.