Check out: http://www.gominekobooks.com/
Here's my collection, and while there are so many better ones by the artists themselves, my priority is the backpiece itself!
Thompson, *Tattoos in Japanese Prints*
Ashcroft and Hori Benny, *Japanese Tattoos: History, Culture, Design*
Cooper, *Tokyo Tattoo 1970*
*Perseverance: Japanese Tattoo Tradition in a Modern World*
Mandelbaum, *Studying Horiyoshi III: A Westerner's Journey into Japanese Tattoo*
Fellman, *The Japanese Tattoo*
Kitamura and Kitamura, *Bushido: Legacies of the Japanese Tattoo*
Kitamura, *Tattoos of the Floating World: Ukiyo-e motifs in the Japanese Tattoo*