It’s a little different in that textbook companies can find authors who may or may not present the information well and then help them with editing and sales.

It’s a little different in that textbook companies can find authors who may or may not present the information well and then help them with editing and sales. Also, in general, the very best books can only be written by a subject expert who can coherently hold enough of the subject in his/her head to find out how to express it. It’s rare but exists (tannenbaums operating systems for example?)