Jumping back to yesterday's first entry, I'll try to pull y'all back from the cliff.
The answer has, at least up until this spring, depended on whether one is suing in California or in New York. The New York court determined that the publisher was not liable for deceptive advertising on the facts described previously, holding that the First Amendment shielded the publisher. A different plaintiff suing in California for the same book, though, won a finding that the publisher was liable for deceptive advertising. Thus, it is definitely in authors' interests to ensure that there are no outright lies on their book covers. Admittedly, this can be somewhat difficult, as the publisher almost always has both title and cover control. To my mind, this reinforces that the California court understood more about the realities of publishing than did the New York court.
The Supreme Court had the opportunity to make this crystal clear, but chose to punt Nike v. Kasky back to the trial court for factfinding. Indirectly, though, the Court at least called the New York court's reasoning into question with a case about fraud in telemarketing. Unwinding that will take a bit more time than I have at the moment. Thus, another goofy cliffhanger.