“All books should be exactly as long as they need to be. There is no ideal length. But like mainstream Hollywood films, nonfiction books have shown a tendency to expand in recent years, for no particular reason. Directors cannot bring a film in at 90 minutes anymore. Likewise, my shelves are overloaded with nonfiction titles that, 30 years ago, would have been 225 or 250 pages. I’m not sure why. Fatter spines do look more imposing, and readers may feel, subconsciously, that $30 should buy them a thick, substantial volume. But time and again, I find, the extra weight comes from empty calories.”