I was a little selfconscious about purchasing/LOVING Twilight as I am not a "young adult", but I figure, it's an awesome book, and as long as you find it entertaining and engaging, stuff whatever age you are.
I have 50 books currently on my bookshelf TBR! It's thanks to a Bookmooch swapping frenzy! I have actually forced myself to not get or borrow any more books for the next 2 years!
I didn't find the actual story of Lord of the Flies nearly as facinating as the ideas and concepts that it presented.
(By the way, I was one of the ones who didn't have to read it at High School.)