Banned Books Week begins with 'Captain Underpants' topping the banned list

It's time to pick up your favorite banned book, because libraries, teachers, anti-censorship activists and book lovers around America are celebrating the nation's most-challenged literature this week.

Banned Books Week, held each year by the American Library Association, hopes to "promote the freedom to choose or the freedom to express one's opinions even if that opinion might be considered unorthodox or unpopular."

Dav Pilkey's "Captain Underpants" series topped this year's list of frequently challenged books because some parents object to its toilet-based sense of humor.

Barbara Stripling, president of the American Library Association, told The Guardian that young-adult books -- like "Thirteen Reasons Why" and "Looking for Alaska" -- often make the list because of the desire to protect teenagers from bad influences.

"Young adult is a big trend right now, and a high number of complaints are directed at those books," Stripling said. "There is a lot of pressure to keep teenagers safe and protected, especially in urban areas, and we are seeing many more complaints about alcohol, smoking, suicide and sexually explicit material."

"Teenagers tell us that they like to read about what's going on," she added.

Here's the ALA's top-10 list of the most-banned books last year:

You can learn more about Banned Books Week on the ALA's website, or visit the Banned Books Week YouTube channel, where authors and celebrities read from their favorite banned books.