While I do like the movie Clockwork Orange I am a bit torn whether it is as great as it could have been or not.
Kubrick obviously used the American version of the book, which was - much to Anthony Burgess' dismay IIRC - edited so Burgess actually calls it "an unfinished version that lacks the intended message".
I don't know if a complete version - like the British book - would have been better, the unfinished version has something to it, I can't deny that.
He also made the violence in the movie more stylized than in the book, where it is much more.... blunt I'd say. An interesting artistic decision that adds some great qualities to the movie. The famous scene with the burglary/rape/murder is a good example.
Regardless of which one you prefer: If you like the movie you should definitely check out the book. It also has a Nadsat dictionary (which you will need. The Nadsat was toned down very much in the movie).
EDIT:
Oh, and fun fact:
Ever since I read the book (or watched the movie, not sure which one was first) I have been calling my Licor 43 con leche "Moloko Plus"
