I understand what you say, but... why not showing at least some screenshots to show the manager and not describe it? Every technical book has this problem, and you can explain that the screenshot correspond to MODX version 2.x . The manager is in constant change, but the basic things are still there. Moreover, EVO and Revo has the same structure, but different look. The book is so big, and I understand that screenshots for everything is not a solution, but.... screenshots for "something" could be fine.
The manager is in constant change, but other aspects of the book can change too.
I miss something discussed in forums some times, and it's advanced templating techniques and other best practices in this area. Maybe for second edition?