Ray Bradbury once said, "There is more than one way to burn a book." A Clockwork Orange,a novella by Anthony Burgess originally published in 1962, did not quite get burned. It's hard to complain about a book that inspired one of the last century's most iconic movies getting mistreated. However, it did, at the very least, get serious fire damage equivalent in its American edition. I recommend you get your hands on the original version, preferably the one with a scathing intro by the author and make your own judgment.
For those not familiar with the work, the story is set in a dystopian society where government is both oppressive and ineffectual. Gangs of teenagers roam the cities, getting high on drugs and terrorizing the inhabitants. The narrator of the story is Alex, a teenage gang leader, who is captured and enrolled into a special program to rid him of his violent tendencies through aversion therapy. The therapy works; however, it does not make Alex a better person but instead makes him physically incapable of violence. Instead of reforming, he loses his ability to act on his still-present violent impulses. Various unpleasantries result, and the reader is left with the lesson that free will is a requirement for a human being's existence, for better or worse.
In the rest of the world the novella was published in it entirety. In the last chapter, Alex, having his free will restored, nevertheless naturally loses his taste for violence and debauchery upon reaching the age of 21. The American publisher rejected this ending as too old fashioned and insisted on cutting off the last chapter, leaving Alex with the same evil tendencies he had at the start. Unfortunately, that's the version used by Kubrick as the basis for the film, and a whole generation of Americans has therefore been misled as to the full meaning of the novella.