"Digital retro" is a very good book of pictures printed in very good paper. It contains lots of high-quality photos of lots of computers, and everything is cleanly arranged. The author has chosen the most significant computers, and I have to say he has done a good work.
That said, I find a great lack of text. For each computer or company, you will only find three or four facts, which is scarce information for not-so-cheap book. You will find a lot more information in Freiberger & Swaine's "Fire in the Valley: The Making-Of of the Personal Computer".
This book definitely remembers me of Christian Wurster's "Computers: An Illustrated History" (Taschen), Michael Nadeau's "Collectible Microcomputers" (Schiffer) or (the Sinclair-centric) Enrico Tedeschi's "Sinclair Archeology" (Hover).
I would recommend you to buy "Digital retro", "Colletible Microcomputers" or "Computers: An Illustrated History" and "Fire in the Valley", and read both side-by-side.