Wally Bock's tip about previewing the books you might want to read has become one of my habits.
It's not fool-proof - on occasion a lemon will slip through - but you usually can spot any gaps between the hype and the substance. Where possible, I scan the book's index to get a sense of substance.
The promotional blurbs on the back should never be taken seriously when considering leadership and management books. There are several big names who frequently gush over the equivalent of swamp land.