Juvenile and school literature are the top targets for attempted book bans.

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From 2005 to 2007, Georgia resident Laura Mallory unsuccessfully attempted to ban Harry Potter books from the libraries in the Gwinnett County school system. The seven-part series about the young wizard by J.K. Rowling ranks as the most challenged set of books since 2000 [source: American Library Association]. Mallory's efforts are among the more than 3,000 challenges against the book based on what opponents perceive to be Satanic undertones.

According to the American Library Association that compiles information on book banning requests annually, parents like Mallory are the most common sources of the complaints. Although frequently banned titles include "The Grapes of Wrath," "Ulysses" and "I Know Why the Caged Bird Sings," juvenile literature like the Harry Potter books receive the most scrutiny. In fact, a majority of book banning cases relate to works found in school libraries rather than in public ones.

Before a book becomes banned, someone must first challenge it. The American Library Association defines a challenge as "an attempt to remove or restrict materials, based upon the objections of a person or group." A successful challenge results in a ban.

Each year, libraries across the United States report hundreds of challenges. The leading causes for contesting a book are sexually explicit content, offensive language and inappropriate subjects for minors [source: American Library Association]. Only a minority of the requests actually make it through to banning the book from its respective library.

When filling their shelves, librarians do not judge the content of books on whether it would be suitable for all audiences. As public institutions, libraries may not discriminate on disseminating information on the basis of age, sex or race, which means that people can check out whatever materials they choose. That said, libraries request that parents and guardians of minors monitor their selections.

Generally, libraries follow content development policies when adding new titles. These policies govern the selection process and are assessed and approved by the library board. Most books have often been reviewed by professional librarians or book discussion groups or requested by patrons.

What is the legal background behind book banning, and why do most challenges dead end? On the next page we'll discuss legal precedents for book bans.