(CNN) Books have long been the source of changing perspectives, but not without some controversy.

In 2018, at least 347 challenges were filed seeking to remove 483 books from libraries or schools, according to a recent news release from the American Library Association (ALA), a sponsor of Banned Books Week, which runs September 22-28.

The annual event started in 1982, the same year the Supreme Court ruled that students' First Amendment rights were violated when Kurt Vonnegut's "Slaughterhouse-Five" and eight other books were removed from school libraries. Since then, books such as the "Harry Potter" series and "The Adventures of Captain Underpants" have made the list.

Despite the legal precedent, schools and libraries still receive formal challenges to remove books from library shelves or nix them from reading lists to protect children from material some people see as inappropriate.

In 2018, more than half the books that drew complaints did so because they contained LGBTQIA+ content, the ALA said. Other reasons include profanity, sexually explicit content, religious viewpoints and materials that candidly portray injustices and inequality experienced by people of color.

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