For decades many books have been banned for a variety of reasons. The resources below contain information on some of the most frequently banned books in the United States. This is not an exhaustive list but just a starting point for further research.
Banned Books Overview - From Credo Reference (from off-campus login with your delaGATE credentials to access this article).
Frequently Banned Titles
This title list contains summaries of books that have been frequently banned or challenged since they were published (from off-campus login with your delaGATE credentials to access this information).