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.
Why is Slaughterhouse-Five being banned in some places? What is supposedly the ‘unacceptable’ content it contains?
If kids learn that war is hell and you’ll come back from it mentally unstable and live like that for the rest of your days then military recruitment guys will have a harder time getting high school kids to sell their souls to the war machine.