It's a resource designed especially for players, although GM's will also find equal use out of it. It updates all of the races that have appeared in Oathbound to 3.5 as well as some of the races that are scheduled to appear in later domain books. (Thanks to Tim Hitchcock, the co-author, Flipper the dolphin is even cool-Dolphin PC's are going to be shapechangers that serve as the ambassadors of their race). It also updates just about all of the classes (a few were omitted and/or greatly modified) to 3.5. Prestige races receive a complete makeover, although I'm not going to reveal all of the mechanical details just yet. Channeling also underwent a drastic transformation including six channeling classes-one tied to each ability. The Player's Guide also provides a bevy of new spells, as well as many of those that appeared in the earlier supplements as well as some applicable spells from Lore of the Gods. We've also incorporated some of the material from Lore of the Gods into a Faiths of the Forge chapter. There is also supplemental information about the various societies prevalent throughout the Forge. Naturally, there's also feats, skills and other goodies for players.
As far as a release date goes, I believe that Steve was hoping for a pdf release sometime around GenCon.