Out-of-print items are often available through second-hand dealers on Amazon.com.
Bergman, Billy and Horn, Richard. Experimental Pop;Frontiers of the Rock Era. Blandford Press, ISBN 0-7137-1550-2. Actually featuring very little about pop or techno-pop acts, for instance dismissing Kraftwerk in a few words, but very good on the minimalists Reich, Riley and Glass, and the early electronic music studios.
Bussy, Pascal. Kraftwerk – Man, Machine and Music. SAF Publishing, ISBN 0946719-38-1. Useful info on the German techno-pop band, though compiled without access to the band itself and perhaps superseded by Wolfgang Fluer’s insider autobiography.
Bussy, Pascal. The Can Book. SAF Publishing, ISBN 0946719055 (1989). Fascinating ...