Time travel is generally considered part of the science fiction genre.
We have gathered a bunch of books that involve time travel from The Magic Tree House to Mal and Chad, A Wrinkle in Time and many more.
Time travel books are almost always filled with lots of adventure. Give them a try!
And if you want to know more about Dr. Who, just below this paragraph is part of the episode where the Doctor explains time. He seems all serious, but then he gets a bit confused.
Do you know of any good time travel books?