A Clockwork Orange is captivating from the moment it begins to the moment it ends. It's disturbing, thought provoking, and often actually quite funny. Stanley Kubrick's keen eye for visuals gets a complete workout, and Malcolm McDowell's performance as Alex is amazing, incredibly dark yet still likable. In case you can't tell, I liked the movie a lot.
The movie begins with several scenes depicting Alex as the leader of a street gang, consisting of him and his "Droogs". They beat up homeless men, fight with rival gangs, and assault women. The latter is depicted in particularly stark style, with Alex bursting into a rendition of "Singin' in the Rain" while his friends hold down a man and Alex cuts off his wife's clothes. Eventually though, he is betrayed and arrested for murder, sending him to jail. That's where the plot really gets going, as he is made subject of a radical and experimental treatment that makes him physically repulsed by thoughts of violence or lust. It seems to do the job, but it raises a lot of questions about free will, and what the actual purpose of the justice system is, and what makes a man good. As I said, it's really interesting stuff, and made all the more entertaining by the performances and Kubrick's direction.
The use of music is perhaps the most memorable element of the film. There's the aforementioned "Singin' in the Rain", but most of the soundtrack is a mix of classical stuff, particularly Alex's favorite "Ludwig van", and some more electronic/synthesizer type-stuff. Also, with Kubrick at his height here, there's just an endless supply of unforgettable imagery. The use of slow motion or fast motion, some well chosen long takes, it's all perfectly appropriate for the scene. Just the opening shot with a slow pullout of Alex's face as he sits in a bar is great. There's not much about the film that isn't enjoyable or at least interesting to watch, unless you find the sexual violence particularly repugnant I guess (it's never very explicit). Dr. Strangelove is still my favorite Kubrick film, but A Clockwork Orange is a nice runner-up.