Chris and Gail Davenport, brother and sister, are transported back to the year 1955 and endeavor to set things straight after they accidentally prevent their parents from meeting
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.