I thought the book was great. It's a quick read, but easily increased what I could do with tmux. I can't think of much more it really needs. Maybe cover stuff like if-shell? The true-color patch might also be worth mention.

FYI, there's a slight bug with the xclip copy binding, but it's pretty easily fixed (bind C-c run "/usr/bin/tmux save-buffer - | /usr/bin/xclip -i -sel clipboard >/dev/null").

Just using tmux to get more than one terminal was really only a fraction of the stuff I could use it for. My terminal launches in XMonad use tmux by default now.

As far as the copy stuff, I'm talking about pipe or line dividers in terminal apps (e.g. mutt, ncmpcpp, etc... If whatever I'm trying to copy covers more than one line, tmux will copy over the divider which is painful.