As long as books have existed, there have been people trying to stop people from reading them. And though the practice is widely condemned, it is also still widely practiced — even in 2016. Today, a spot on the American Library Association's banned books list is essentially proof positive that the title is worth reading.
Every year, the ALA compiles a list of books that have had formal bans enacted or requests to ban filed against them. (Though the ALA notes that it's likely the majority of challenges go unreported.) The reasons for removing any particular book from the shelves of a school or library are many and varied, but the most common have to do with sexual or profane content that corrupts youth, destroys family values, and defies organized religion.
But as Judy Blume — a regular on the list of the most frequently banned authors — put it, "Something will be offensive to someone in every book, so you've got to fight it." Oh, and banning a book is giving a big middle finger to the First Amendment. In the words of former Supreme Court Justice and civil liberties activist William O. Douglas, "Restriction of free thought and free speech is the most dangerous of all subversions. It is the one un-American act that could most easily defeat us."