The Seymour Cray Era of Supercomputers

I just finished the book above, and it was a very interesting read
(especially since I worked with these machines around the era the
authors describe, from ~1960 to 1996, ended).

Well worth reading.  Architectural details are not the main focus
of the book; rather, it deals with Seymour Cray's work, but also
with the technical reasons why some architectures were more
successful than others, and how these machines were adopted
and used at different customers.

ISBN  979-8400713705.  I bought it on Amazon.