I agree that many business books have a good ten to twenty page article trapped inside, with the book length writing required as packaging for sale. Some books, e.g. Innovator's Dilemma, offer a detailed review of examples that help to reinforce the basic concepts (as distinct from a collection of personal anecdotes and reminiscences).
... and for future consulting work, in some cases:-)
Yeah, with the good ones, it's not like the rest of it is just "garbage", and I enjoy reading them, but I think for people who just want to know what the 'big idea' is, you don't need the extras.