It's a superb book - interesting, well researched, easy to read and, above all, provides a background for understanding how Carmack and Romero each ended up where they are now.

+1 - This book actually rekindled my love for gaming and reminded me of the passion for computers that contributed to me deciding to become a developer in the first place.

Also shatters the popular idea of Carmack as a nerd (he breaks into a high school and steals computers as a youth) an Romero as a bro (he's writing a bunch of games, compression tools and other useful bits and pieces)

I HIGHLY recommend reading this book. I've had it since ~2004, and read it 6 or 7 times. It's such an enjoyable experience, and if you develop software and/or software companies...still very relevant.