An interesting read. Some of it is repetitive, the book might be shorter without much loss - lots of inspirational paragrapgs repeating the message of each chapter at the end of each chapter.
I don't know much about screenwriting (having read only William Goldman's books, which touch on the subject), but this book seems to be full of useful, concrete advice. Advice, that is, how to write a screenplay that you can successfully sell. Not good screenplays necessarily, and not with an eye towards good films, just things you will be able to sell, apparently, written according to formula. True, formulaic films can be good or bad, and I prefer them good, but they all sound very predictable and there are so many films that are more interesting.