Save the Cat has quite a reputation in the writing community, both for screenwriters and novelists, and now that I've finally read it, it's not hard to see why. It lays out structure in such a clear, easy-to-understand way, and even if you've written lots of stuff before, it makes all the rules you know and rely on all the sharper.
Screenwriters live and breathe structure, but novelists and short story writers, not so much. At least we're not told to. Creative writing classes, from high school through college and beyond, often focus on the prose, itself. They tell you to show instead of tell, to make the dialogue natural and conversational, to avoid cliches and trite phrasing, to not be so heavy-handed, etc., etc. This is all well and good, but this is all part of polishing. Making the words themselves beautiful, engaging, honest. This all assumes that you know how to craft a story in the first place.
Which so many of us struggle with. In fact, many of us get the advice that we should just write the story as it naturally comes to us and not get bogged down in structure and rules. It's literature, after all! Art!
That's why I love this quote of Blake Snyder's. You can break the rules. You can turn them upside down and defy cliche. But it's a lot easier to do once you know and can articulate exactly what those rules are.