An Amazon Mystery
The hardback edition of The Substance of Style costs $15.72 and takes a long time to ship (currently listed as "ships within 1 to 2 months"). The paperback edition costs $10.46 and ships in 24 hours. (The paperback also includes some additional material, though you can't tell that from the Amazon page.) Yet the hardback is consistently ranked much lower on Amazon than the paperback, though they generally move up and down together. Why? The best I can guess is that you can go to the bookstore and buy the paperback, while the hardback is harder to find.