It's strange. You'd never guess that a book based on a screenplay could be any good, but you'd be wrong in this case.
Craig Shaw Gardner, my favorite movie-tie-in author, wrote this book, taking a good screenplay and turning it into a truly masterful, exciting, and touching book!
To start off with, the book has whole sections that were cut from the film, giving it more depth and character development. Hmmm.... character development.... there's a whole lot of it. The book truly gets inside the head of everyone, Batman, The Joker, Alexander Knox, Commisioner Gordon, and even Vicki Vale, and all have varied outlooks on the book's events. The Joker sees everything as hilarious, and twisted, Vicki's stressful situations are more developed, Knox is detailed as a hard-boiled reporter (Moreso then the film), Commisioner Gordon is very interesting, in the fact that he likes Batman, but is sworn to his duty to arrest the vigilante, and he's very dedicated and tough, and Batman/Bruce is incredibly written. The writing for Batman's mind is at it's best toward the end, when Batman tries to get up into the Cathedral, while trying not to faint from the wounds he got by crashing the Batwing, and he fades in and out of reality as he remembers the night he lost his parents.
I mean, the film is excellent, but the book is not to be missed. It's deep, profound, moving, and truly exciting in the way Gardner writes fight scenes. Fast and furious, but also surprisingly detailed. I've read this thing so many times that the pages are starting to fall out, and I am continually surprised at the quality of the book. A truly enjoyable read from start to finish.
If you're a fan in the least, you'll pick up this wonderful book!