In an annual rite of National Library Week, the American Library Association Office for Intellectual Freedom this week released its Top Ten List of Frequently Challenged Books, this year led by children's book series Captain Underpants, by Dav Pilkey. Compiled annually by the ALA, the list collects "reports on book challenges from librarians, teachers, concerned individuals and press reports." A challenge is defined as a "formal, written complaint filed with a library or school requesting that a book or other material be restricted or removed because of its content or appropriateness."

In 2013, the OIF said it counted 307 reports of attempts to remove or restrict materials from school curricula and library bookshelves. The good news: this is down sharply from 2012 totals, which logged 464 attempts. The full top 10 list includes:

1) Captain Underpants (series), by Dav Pilkey (Reasons: Offensive language, unsuited for age group, violence.)

2) The Bluest Eye, by Toni Morrison (Reasons: Offensive language, sexually explicit, unsuited to age group, violence.)

3) The Absolutely True Diary of a Part-Time Indian, by Sherman Alexie (Reasons: Drugs/alcohol/smoking, offensive language, racism, sexually explicit, unsuited to age group.)

4) Fifty Shades of Grey, by E.L. James (Reasons: Nudity, offensive language, religious viewpoint, sexually explicit, unsuited to age group.)

5) The Hunger Games, by Suzanne Collins (Reasons: Religious viewpoint, unsuited to age group.)

6) A Bad Boy Can Be Good for a Girl, by Tanya Lee Stone (Reasons: Drugs/alcohol/smoking, nudity, offensive language, sexually explicit.)

7) Looking for Alaska, by John Green (Reasons: Drugs/alcohol/smoking, sexually explicit, unsuited to age group.)

8) The Perks of Being a Wallflower, by Stephen Chbosky (Reasons: drugs/alcohol/smoking, homosexuality, sexually explicit, unsuited to age group.)

9) Bless Me Ultima, by Rudolfo Anaya (Reasons: Occult/Satanism, offensive language, religious viewpoint, sexually explicit.

10) Bone (series), by Jeff Smith (Reasons: Political viewpoint, racism, violence.)