Advice to Technical Writers
http://tog.acm.org/resources/RTNews/html/rtnv9n2.html

Tognazzini, Bruce
Ray Tracing News
1996

Abstract:

A friend asked the going rate for author's royalties on a technical or trade paperback, so I asked some people what they received. A few wrote back with extremely enlightening and fascinating comments. I passed these notes on to other authors, and received yet more interesting reading back. I have now edited all these comments down a bit, mostly taking out the names of authors and publishers and removing publisher specific comments.