Yup—we definitely have a YA book on our hands with this one.
When it comes to the science fiction bit, though, you might be a little confused. Facebook is real, after all, and it's not like there are aliens up in the mix or anything like that. But since the book is set in the 1990s, for our characters, Facebook is a blast from the future—something they've gained access to against all odds. And for this reason, we're saying The Future of Us dabbles in sci-fi. After all, how else can we explain what happens?