Where can I buy this?

[Shovah32]

As far as I know there are no stores or direct download services selling dominions.
Buy the game from somewhere near to you if you want to lessen the wait(find a nearby seller on amazon for example) if needed or just order it from sharpnel.

I could be wrong but mail order, as far as I know, is the only way to get the game.
This game is great - you will not regret buying it. Just make sure to ask any questions you have on these forums, it helps quite alot as the game(as you have probably noticed) is rather deep and complex.

edit: Just keep playing the demo for now to get used to using national troops and lower-tier spells. There's quite a bit of stuff you can do in the demo while you wait.