Martin Guitars: A History is a beautiful collection of photographs and stories of individual instruments, as well as the amazing history of CF Martin & Company, designers of the worlds most recognized acoustic guitar, the dreadnought.
This book has hundreds of pictures of beautiful, rare guitars. While the pictures are enough for me, the story of the Martin guitar company is well worth reading. Written by journalist Richard Johnston & Martin's Dick Boak, you'll find guitar minutia presented in a gleeful way. These guys love guitars.
There is also a technical reference as second volume, which offers neat insight as to how the braces and their various shapes over the years effect the sound and durability of these famous guitars. Also pages on how necks are affixed. It is quite detailed.
I'm a huge Martin fan, I live with a D-15 and an HD-28. They keep my GAS under control. This book helps me admire guitars without buying more guitars.