The game has two core books. The first, A Song of Ice and Fire Roleplaying, provides the rules. It covers everything from character and house creation to intrigue and mass combat. The second book, A Song of Ice and Fire Campaign Guide, describes Westeros in lavish detail, providing full details on all the major regions and principal players of the game of thrones.
That separation is nice, especially for those folks who might want a sourcebook for the novels, but are not all that interested in RPG rules. I certainly could use a handy guide to keep straight who is who.
The game is going to be based around a new and unique engine, rather than being OGL or a derivative of one of Green Ronin's existing RPG systems. Robert J. Schwalb teases us with a few tidbits in the first Designer Journal entry:
These sorts of discussions led into other areas, from which we derived a number of precepts that were more or less followed until the end of the design process. We wanted the learning curve to be low to make the game appealing to a broader range of players, but without sacrificing the depth of game design in order to retain those gamers that prefer a more mechanical approach. We also wanted a game robust enough to address all levels of society, from nobles to the lowliest of smallfolk. SIFRP needed a game engine to handle combat, intrigue, and warfare simply and without becoming tangled up in a lot of complex rules. SIFRP also needed to support just about any play style, from bands of adventurers prowling the ruins of lost civilizations in search of fabulous treasures (old-fashioned door-kicking, monster-slaying, treasure-stealing fantasy), to complex struggles fought using diplomacy and treachery in the shadow of the Iron Throne (a far more appropriate sort of game in keeping with the novels). The game needed to handle the clash of armies, the brutal and bloody skirmishes of a mist-shrouded forest, and the splintering of lances before roaring crowds at one of King Robert's tournaments. A tall order to be sure, but these, among other elements, were central to our thinking as we hammered out the mechanisms that would drive the game forward.
Right now, that reads an awful lot like the typical all-things-to-all-people press release you get early on in the life of a product. That said, I don't doubt for a minute that the folks at Green Ronin do, in fact, have that sort of broad flexibility as a firm goal. It'll be interesting to see how the final product works.