The Amazon blurb is somewhat out of date (and damned if I can get them to change it!). Of Gods and Mortals (OGAM) is based on the Song of Blades and Heroes system, but introduces new mechanics and rules to make it stand apart from that predecessor.
Warbands are smallish affairs, with a God leading the force, a few Legends, and a couple of units of 4–8 Mortals being the norm – e.g. Thor, Fenrir, a Dvergar Weaponsmith, two Valkyries, a unit of 8 berserkers and a unit of 4 skirmishers.
Changes since the Amazon blurb include the reworking of the faith system as mentioned above – there's no tracking of levels or faith points, but the interplay between Gods, Legends and Mortals remains, and each must rely on the other to work effectively.
The rulebook contains Celt, Greek, Norse and Egyptian lists (totalling 37 Gods, 45 Legends and 53 Mortal units). The 'missing four' (Chinese, Japanese, Aztec and Pre-Islamic Arab) haven't really been forgotten (I know for a fact at least two are fully developed, so keep an eye out closer to the October release date). As suggested above, this reduction was due to space constraints, but we did make sure that the book includes a full unit builder that allows you to stat up your own pantheons, adjust existing units you think should be represented differently, and create whatever new units you like.
Fomorians and Dvergar ARE already included in the book, so those two cracking armies shown above should be really easy to field.
There's some more detailed discussion, including an example of unit creation, and some photos of more sample warbands and the forthcoming North Star OGAM figures here: link
That's splendid news to me.