The first thing that comes to mind is my teenage love for the first three Dune books and how I tried to reread the first one when the movie adaptation came out a few years ago and I was like, "Wow, Herbert thinks this book is so deep and it's really just not." The pretentious and self-satisfied aura of it went right over my head as a kid but was enough to make me set it down after a few chapters as an adult.

The flip side of this is books that I didn't enjoy in my early teen years that I think I would appreciate a lot as an adult. I need to reread The Scarlet Letter and see if I still hate it--I bet I wouldn't!

(I'm super fascinated by your experience with finding books more scary as an adult. The written word doesn't scare me--it can hold me in suspense or appall me, but I just...don't get scared reading books.)