I wouldn't call it a book but it's surprisingly an easy read, straight and to the point. It's well structured and ordered and explains everything in simple terms, making things easy to understand.
As others say it's a gem, and it could use a bit of polish bringing it up to date with thr current state of the art.
It's essential reading to anyone in tech, especially web developers, networking people, admins, even those who think they understand how things work.