How difficult is this game?

[Micah]

Check out the tutorial as well, though I would recommend reading the manual at some point as well. One caveat to that though, is that some things in the manual have changed since it was written (that's a nice way of saying that they're buggy). So take everything with a grain of salt and chalk it up to learning when you find something that diverges from the printed material, it'll save you some frustration to keep that in mind (speaking from personal experience here).

Some things off the top of my head:
Your rate of dominion spread does not increase with every 5 temples you build.
The morale system is (I'm pretty sure) much more complex than the rulebook explanation, you don't get random routing of elite units due to a bad morale roll. (Which I'm glad is the case)
Critical hits due to fatigue do not simply halve the protection value of the unit when they occur, the effect is much more severe in practice.

There's other stuff in there I'm sure, but that's a sampling. Don't mean to scare you off, as this is without the doubt the best money I've spent in my life on a game, just wanted to keep you from taking everything in the book as gospel.