On two related tangents I'd suggest on the one hand the 3cd compo Ohm-the early gurus of electronic music1948-1980 which has selections from Reich, Riley, Oliveros amongst others. It places the Minimalist composers in an electronic framework rather than a classical one. It effectively points out that to achieve the levels of precision required in the composition, traditional instrumention takes a backseat to mechanical/electronic approaches. The essays and interviews from the 96 page booklet accompanying it may be found here. http://www.furious.com/perfect/ohm/index.html Well worth hunting down.
On the other I'd recommend David Toop's Ocean of Sound, both the book and the two cd compo (sadly out of print). These place the minimalists in an ambient context which echoes some of Steve Reich's view on his music reflecting the industrial nature of post-war America. The book also illustrates how other non-western music impacted on the conception and construction of ambient musics. The cd is one of the best constructed compilations created and has been mastered so that each track segues into the next.
Both of these approaches show how minimalism impacted music from elements other than compostional, being instrumentation and environment.
regards,
Giles