Smalltalk 80: Bits of History, Words of Advice edited by GlenKrasner. ISBN: 0201116693 .
Available online: http://www.iam.unibe.ch/~ducasse/FreeBooks/BitsOfHistory/
Alternately "Postscript Language Program Design", one of the four standard references on PostScript. The other three official guides are known as the Blue Book, the Red Book, and the White Book.