Masterbook (1994)

From the introduction in the book:

Masterbook is a master game system published by West End Games. This system can be used to roleplay in virtually any game universe, with virtually any options, but it is also designed to be used with specific game settings designed by West End Games.

Each game WorldBook will provide additional information on each of the new fictional settings, but every MasterBook world follows the core set of rules set down in this volume

MasterBook was acquired by Precis Intermedia when the West End Games were sold off and is being reprinted from the originals.