Well, I just thought of another book I wished I hadn't finished:
The Catcher in the Rye. I actually read it twice. The first time I read I was in the 9th grade and thought Holden was so deep and his angst such an example of what is wrong with our materialistic and fake modern society. I read it again two years later and wondered why I ever found that character appealing. He came off as such a spoiled brat. I still wonder why my opinion of the book changed so drastically.