The "Harry Potter" series, John Steinbeck's Of Mice and Men and Maya Angelou's I Know Why the Caged Bird Sings were among the 10 books most "challenged" last year as appropriate for schools and libraries, according to the American Library Association.

The list coincides with the 20th annual Banned Books Week, which ends Sunday.

"Banned Books Week serves to raise awareness about censorship and remind Americans that our freedoms can be fragile if we are not vigilant in protecting them," Judith Krug, director of the ALA's Office for Intellectual Freedom, said Wednesday.

The ALA defines a "challenge" as a formal, written complaint filed with a school library about a book's content or appropriateness.

Criticisms, usually by parents, include Satanism (the Potter series), offensive language and violence (Of Mice and Men) and racism and sexual content (I Know Why the Caged Bird Sings).

The ALA reports 646 challenges in 2000, up from 472 in 1999, and believes this represents just a fraction of actual complaints. Krug said books, however, rarely end up being pulled.

The list is also sponsored by the American Society of Journalists and Authors and the Association of American Publishers.

Included are Robert Cormier's The Chocolate War, cited for violence and offensive language, and Caroline Cooney's The Terrorist, controversial well before the Sept. 11 hijackings.

The Terrorist is a young adult novel about a boy killed after being handed an explosive package on a London train.

"The complaints are because the alleged terrorist is an Arab," Krug said.