Banned Books Week is an annual event, typically held during the last week of September to early October, that highlights the freedom and open access to information, especially through libraries.
This celebratory week brings libraries, booksellers, storefronts, publishers, authors, journalists, researchers, and individual readers together to celebrate all things books - especially books considered "unorthodox", "unpopular", or "problematic".
The American Library Association has resources, book lists, and history on Banned and Challenged Books in America.
A challenge is an attempt, usually formalized through a request slip or verbal request, to remove and/or restrict materials, based upon the objections of a person or group. A banning is the removal of said material from a collection, or from public use.
A central fact is that challenges do not simply involve a person expressing preference or reinforcing a singular point of view; rather, they are an attempt to remove material from the curriculum (e.g. at a community college) or library, thereby restricting the access of others. They are a threat to freedom of speech and choice.