On principle, I want to give this book 5 stars. If you buy it, as I did, you will certainly not be disappointed. I, like many of the other reviewers, have an issue with that this book is supposed to be; "The Art of The Dark Knight". This isn't an art book; it's a combination of an art book and the screenplay; but not the final shooting script as far as I can assess. One nice detail, however, about the script is that effort has been put into the presentation of the script, with the pages littered with shots from the corresponding scenes alongside the script itself. There are a few differences between the script and what was executed by the cast, but overall it's very similar. If you loved this movie, then there is no reason why you shouldn't get this. It's a big, heavy book perfect for coffee tables, which is most likely where you'll want to keep it face down due to the superb back cover taken from one of the movies posters; namely that featuring Batman doing a wheelie on the Batpod. The quality of the photos is top notch, as is the page quality. Also, for this price it is very reasonable.
If you want a final selling point; this book is worth it's price alone almost solely for the early concept drawings and computer-generated images of The Joker. From original concept to execution, the evolutionary process is quite staggering. The original Joker concept looks more suited to David Tennant than to Heath Ledger. One disappointing thing though is that I didn't think that enough attention had been paid to the transformation of Harvey Dent (Aaron Eckhart) into Two-Face.
In closing, if you are buying this book solely as an art book, then you may be disappointed. It really lacks substance in this regard, with only about 60 pages of artwork and limited text before it launches into the script. However, if you're buying it out of interest for the film as a whole; then this book is a great addition to your collection, and a very good companion piece to the film.