A Matter of Oaths, by Helen S. Wright; copyright 1990; ISBN 0-445-20983-6.
I saw this recommended on the Internet somewhere, in August or July probably, and bought a copy used. It was good. Then, in the end of September or the 1st or 2nd of October I was looking in boxes of books in my garage, and say I already owned a copy. I can't say I remember the contents, so I may have just never read it before now.
Random musings on books, code, and tabletop games.