From the introductary paragraph:
"This Chaosium Monograph work is a setting book for adventuring in Michael Moorcock's Hawkmoon. It is neither a game in its own right nor a sourcebook in the traditional manner. Instead, this work is a distillation of a much larger, more complete sourcebook that will, we hope, see physical print at some time in the future [It didn't]. The monograph series from Chaosium allows us to get at least the core of the Hawkmoon sourcebook into print, in a way that (we hope) satisfies most people. But for that to happen, we've had to make compromises - and we'd therefore ask of you to bear with us, and work with us by filling in the rules mechanics and system-specific gaps in a way that suits your players and your campaign style. The tools to do this already exist - in Chaosium's Stormbringer 5th Edition and the Basic Roleplaying Players' Book. Applying the mechanics from either or both of these superb resources should not be difficult for most gamemasters."