"The War of Art," if anyone needs a source.
EDIT: Hmmm... On checking the foreword again, I see it says that book one is actually "Defining the Enemy". I'm starting to think that these 3 "books" are actually sections of the physical book. I guess the physical book "Turning Pro" of the same author might be completely unrelated to the equally named book two the foreword mentions. That's pretty confusing if true.
As it happens I was looking at the book the other day and decided not to buy it. Maybe I should take another look.