I like that it is simple and straightforward. It breaks down the progression of a story, and gives a template that can be used interchangeably for different types of stories
As a simple guide with worked example (Romeo and Juliet), this is a pretty good resource for beginner writers wanting something straightforward to practice with - as long as they don't think this is the be-all and end-all of it!
Basically this book presents a working outline on which to hang stories that potential writers want to write. A guide is always useful as long as a person feels free to vary the route.
I'm planning on participating in National Novel Writing Month, and this book helped me actually complete my storyline! I highly recommend it to anyone who has no idea what they're doing when writing fiction.