One of the more recently published books on this list, The Perks of Being a Wallflower by Stephen Chbosky ($7) follows introvert Charlie as he tries to make it through the trials of high school. Readers find themselves inside Charlie's mind, which, though just a freshman in high school, does not shy away from the tough questions about drugs, sexuality, masturbation, and mental health. This is precisely what got the book banned from school districts, particularly in 2009, when it was one of the most challenged of that year.