Absolutely my favorite book when I was young. I picked it up hoping for some similarity to the Back to the Future films. I didn't learn until years later that this very book served as a loose inspiration for the screenwriters on first film of the BTTF series. It's still a great book on its own merits as well.
80s teen (two of them, in this case) travel through time to the 50s and accidentally interfere with the parents first meeting and then has to fix said thwarted meeting before their very existence is erased and then make it back home to, well, the future.
If that sounds familiar to you, then you'll probably agree the screenwriters of the version of this story you're no doubt familiar with owe this author some royalties.