How is the book ending different from the movie ending?
Depends on which version of the book you get. The original British pressing has 21 chapters, the American version only has 20, missing the last chapter in which Alex grows up starts thinking about having kids and leaving his crazy life. For whatever reason Kubrick’s movie is the “American” version even though he was in England at the time and probably had the British pressing.
the movie fades to black... the book turns to a blank.
there you have it.
The 21st chapter was omitted from the editions published in the United States prior to 1986.In the introduction to the updated American text (these newer editions include the missing 21st chapter), Burgess explains that when he first brought the book to an American publisher, he was told that U.S. audiences would never go for the final chapter, in which Alex sees the error of his ways, decides he has simply gotten bored of violence and resolves to turn his life around.
At the American publisher's insistence, Burgess allowed their editors to cut the redeeming final chapter from the U.S. version, so that the tale would end on a darker note, with Alex becoming his old, ultraviolent self again – an ending which the publisher insisted would be "more realistic" and appealing to a US audience.
The film adaptation, directed by Stanley Kubrick, is based on the American edition of the book (which Burgess considered to be "badly flawed").
Kubrick called Chapter 21 "an extra chapter" and claimed that he had not read the original version until he had virtually finished the screenplay and that he had never given serious consideration to using it.
In Kubrick's opinion – as in the opinion of other readers, including the original American editor – the final chapter was unconvincing and inconsistent with the book.