One of the big classification schemes for books is called BISAC (Book Industry Standards and Communications Subject Headings). Amazon uses it. It gives us headings like Nonfiction>Law>Agricultural, and Fiction>Christian>Historical.
Did you know that"YA>time-travel" is an actual subject heading on BISAC? BISAC code YAF063000. No kidding. An entire young-adult subgenre devoted to time travel. It's that popular.
So what's the deal, aside from Doctor Who? Why is this as appealing as vampires and zombies?
Because if you're over 30, you've already experienced time travel.
Think about it, my fellow gerontonauts. And welcome to the future.