Here are some books about early Macintosh computers based on the 680x0 family (not PowerPC or Intel). Most are out of print, but used copies can be found (usually quite cheaply) at places such as: Amazon, Barnes & Noble, Alibris, Abebooks, Half, Powell's, and Biblio.
For each book I have provided an Amazon link. If you buy a book through this link, a small percentage goes to help the Gryphel Project.
More importantly, buying these books may help to preserve them.
Some can be downloaded for free. A link is given when I know of one.
This list only contains English language books that have ISBN numbers.