I read this when I was around 22 or 23. I can't remember if I read it because I'd seen the movie, or because I wanted to see the movie. It seems most likely that I saw the movie first.
I recommend the book over the film. And I like the film very much. It is the Stanley Kubrick film that I enjoy watching the most. Specifically, my other top Kubrick films - Dr. Strangelove, 2001: A Space Odyssey, Full Metal Jacket -I often watch because they are meaningful to art, and film, and some Big World Thing. They are good films, but they are big and meaningful and take a bit of commitment to watch in full.
But Clockwork Orange, I just plain like (draw what assumptions you like). I like the white, mod world that Alex inhabits. I like the droog fashion. I like Malcolm McDowell's smirking, vicious Alex. It's a fun movie, although I don't think Kubrick intended it to be fun. I'm not the only one who delights in it: a brief Internet search turns up Clockwork Orange t-shirts, posters, and even a really expensive (but quite lovely) Clockwork Orange Ludwig Van bust. At sci fi conventions and Halloween parties, you can see attractive young ladies in Clockwork Orange costumes.
See, fun. It's not just me!
Which is the difference with the book. In writing this, I tried to explain this difference a few ways, and all of them came out making the book sound boring by comparison, which is not the case. When it comes down to it, I think the movie is punk. Punk criticizes without offering a solution. Punk is entertaining, but also chaotic, anarchistic. So the film is fun to watch, but I don't want to live in Alex's world. I can only handle his existence as a caricature of my world.
The book is more classic. Although Alex's world in the book is just as chaotic, Anthony Burgess put very specific structure around it. It has 3 parts, with 7 chapters each. And the book does, eventually, come to a resolution, unlike the film. The problem of Alex - that he can only be a consciousless menace or a defenseless victim - is resolved in the book. As much as I enjoy the punk version of the story, I feel more satisfied at the resolution of the classic telling.
For that reason, the book makes me feel a little less guilty about liking it.
If you decide to read it, make sure it includes the 21st chapter. The film leaves out the final chapter, and many American printings of the book do as well.