The most challenged book of 2014 was a mere third in 2013. What was the most challenged book that year? I'm glad you asked!
Captain Underpants (series), by Dav Pilkey
Reasons: Offensive language, unsuited for age group, violence
No, I am not somehow mistaken. As a matter of fact, this was the most challenged book for two consecutive years, 2012 & 2013.
In 2013 alone, there were 307 attempts to remove or restrict books from school curricula and libraries. And that's just the reported challenges. The ALA estimates that there are 5 actual challenges for every one made formal. And in 2012, Captain Underpants beat out 50 Shades of Grey! Go figure...
The author's response is wonderful:
LOVE this response! Do me a favor, and buy the first book in the series of Captain Underpants, just to add to your collection!