I've read the book as well. I'm not sure what to make of it in terms of why id went the way it did. Anyway, Carmack remained, and after Romero left I believe he had a leading role in id. Yet he seemed to remain isolated in his principle of opening up his code now and then. Since Carmack has left id has been a fully closed house of software. Pretty sad. At the same time, I dont care since they did not make any notable game recently anyway.