CADCIM Technologies has a Pro/E book as well. It has the most info I have seen in a publication yet, and for being in a tutorial driven format, it isn't too bad. What we really need is for PTC to publish a very good Command Reference Manual. One the has all of their functions listed, along with a full description of each option. Dassault used to have one for CATIA v4 when I was using it years ago, and I have always wanted one as comprehensive for Pro/E.
PTC used to have a command reference up to 18 or 2000i, but then so did Excel and Word. Turns out, most people don't like to read manuals, so they stopped publishing them. Also, it eats into selling training.