Maybe it is tradition, but most RPGs based on Michael Moorcock's worlds are based on Chaosium simple system. This last incarnation is no exception, being based on Runequest 4.
This book replaces the RQ core (and probably the companion as well, considering the limited magic accesible to players in the setting) with a much more useable information. It still assumes more than a passing knowledge of the described world, but that is a logical assumption.
Unlike the Core rules, it is possible to play perfectly with only this book, which is a very good thing in my opinion.
The mechanics are the well thought, streamlined system from RQ4, and they fit quite well the power level of the novels.
A well done adaptation of the setting with a well fitted system, maybe lacking some background but nothing a good read of the original source cannot solve.