Well, books are different than appliances, and publishers can suck at marketing as bad as any other industry! But usually, a book's title and cover will give you some clue as to the mood, and if it's a new author and Stephen King says "A creepy masterpiece of bloody horror from a stunning new voice in fiction", you'll generally get a sense of genre anyway. If I spotted a book and the only blurb was Cormac McCarthy calling it "fantastic", that may be all I'd need though.

I do wonder about hardcover releases with very little info; publications haven't reviewed it yet, but if a publisher feels a book may do well, as I understand it they reach out to other authors they publish to read & provide a quote. Though usually a hardcover has a paragraph outlining the book on the inner dust flap; I don't see many paperbacks without a quick description of the story on the back though.