It's easier to focus and learn on dead trees. For the author it's an interesting model too. Posting online, especially "beta" versions, gets you fast feedback a

It's easier to focus and learn on dead trees. For the author it's an interesting model too. Posting online, especially "beta" versions, gets you fast feedback and ultimately a better book. The paper sales are essentially a tip mechanism. I am not allowed to sell "Mature Optimization" because it's owned by my former employer, but I had some nice bound copies made as gifts for people who come to talks.