Time and the evolution of the game is changing my view on how the Core Rules are best presented. While I am still so into the Cook/Moldvay/Marsh idea of the successive sets and their cover-within-a-cover scheme for each successive set, I've had to drop that in favor of putting all of the player's infomation into one book and the Referee's information into another. The upside is that individually each book is going to be geared towards what information is needed by each to play and now I can cram more things into them both without bleed-over of information.
This also means that there will be no 'Companion' volume either (at least where the rules are concerned). The Core Player's Guide and Core Referee's Guide will have the information for levels 1-25 for both Referees and players, including higher level spells. Also included is the Barbarian class that was slated for the Companion and a new player character race, the Asarlai, more Fighting-man Combat Options more monsters, magic items and Referee advice and guidelines for running their games.
Stay Tuned for more exact details!