Steve Clark's Sigmac reference guides were a great reference tool. I have my copy of them here and still refer to them occasionally. They were written in the ARRIS 6.04 time frame. While this is quite old, much of the reference information on Sigmac has not changed that much.
For the $ utilities, there are several that have changed and several new ones since then. We have made our internal documentation on $ utilities which is up to date public. The documentation on all 635 $ utilities may be found on-line at www.arriscad.com/developer
. This basically renders the volume 2 of Steve's books obsolete, except that he does still have good information on system flags and a few handy references such as an ascii table.