I have given this a quick read (4 hours).
Great so far. All the rules should absolutely give any campaign an 'ancient' feel. A treat if you want to break out of the usual 'high fantasy' setting.
The new combat rules (shield parry, armor damage reduction, active defense, etc) are great. The new Unearthed Arcana book for d20 have given similar options, but I really like Mongoose's version better.
A highlight: the healing, and grievous wounds. A great (and easy) game mechanic to do this. I almost cringed when the book described wound cautery

. These rules really lend themselves to an 'ancient' campaign: no one would venture too far from a center of healing (cities). You sure won't last long going 100's of miles away in an unexplored swamp :shock:
The magic & miracles section was done well. It should give a nice flavour to any campaign. It will need to be play-tested before I can judge the balance.
I have one concern about it already: Witchcraft and Hekau spells are powered by a character's hit points (fine - nice idea). BUT....
I see a few witches and Egyptian priest's taking a level or two in a Fighter class, just to boost their Hit Points so they can cast more spells. This does not seem right....
(Please note: the auther does point out that multi-classing should be rare)
There was a nice write-up on the Greek and Egyptian gods. This section could have used a better explination of the fields used when describing the deities (e.g.: it took some looking to find out exactly how the 'disfavour' or 'virtues' mechanics works in the game).
Again, the added bits like: sacrifices, etc will really add an 'ancient' touch to any campaign.
For example, I can now see characters running through a market, looking for some sheep to sacrifice on the docks, to Poseidon, just before a long sea voyage.
Great Job. I can't wait to use this book!