IMO you need both. Some things might take years to learn, or might never be learned, that a seasoned pro can tell you in a book in however long it takes to read it. But I doubt that anyone could read any amount of books and sit down in a good, solid hold 'em game and clean house. More likely, they'd have their house cleaned.

Books are good for theory and abstract concepts... experience gives you instincts and your "sea legs," so to speak.