Dan (the man), my favourite novelization of a movie or play is my own for my film DRAGONHEART. It is actually more a novel than a novelization because I tried to write a real book and not one of those 150 page we-put-the-screenplay-in-past-tense jobs. It also is in many ways vastly different than the film, because I was able to take out crap that had gotten put in that I didn't want and restored things that had gotten taken out. I worked from seven different drafts of the script. I also just came up with lots of scenes and inspirations that weren't in any version of the screenplay.
The great luxury of writing the novel was that I realized I didn't have to stop a scene after three or four pages and that I could go on. I could also just luxuriate in the language and prose. It was fun to crawl inside various characters' head and do a chapter or scene from their point-of-view, oft times a rather minor character. I got to see the galleys and correct any stylistic touch of mine that might have gotten changed. It was the greatest writing experience of my life. The book is the definitive version of Dragonheart. It did very well in the market, going into five printings and making me a considerable chunk of change. It probably would have done even better had the movie done better at the box-office.