Finally someone who understand teens.
No No No No No books for high school grads! And most of the ones named here would be better saved for Grandpa for Father's Day. Teens would rather have Underwear than a book, but that isn't a suggestion either.
Gift certificates for sure! And NOT to the Book Store!
Well MAYBE the Dr. Suess book, if you insist on a book, but money {even a buck} would be appreciated a lot more.