Just scratching the surface...
"Digital at Work", by Jamie Parker Pearson, ed.
the best single history of Digital.
"A Computer Perspective", by Eames
cool illustrated Timeline that was sponsored by IBM.
"Computer Lib / Dream Machines" by Ted Nelson
about computing in the 1970's by the hypertext guy.
"Digital Deli" by Steve Ditlea
gets into deeper detail than Nelson's work.
"A guide to collecting computers and computer collectibles",
by Kevin Stumpf. quirky, quirky.
remember: "Collectible Microcomputers", by Michael Nadeau
"Planning A Computer System" as was just mentioned is an excellent find.
John A.