Very similar to HoMM with turn based combat. Gorgeous graphics, nice storyline and several nice touches bring the genre bang up to date.
Lots of spells, monsters and places to see. The ability to return to places you've been before and continue to interact with NPCs is a nice touch.
Having wives and children was unexpected and surprisingly useful!
Play as a warrior (pure combat), mage (pure magic) or paladin (a bit of both).
Nice shortcuts around the gameworld using derigibles, ships and even trains.
Still playing it and not finished after over 30 hours of gameplay.
At the price it's a steal - my only complaint is that there's no sign of any expansion yet!
In short, if you like TBSGs, buy it!!
(By the way, it's NOTHING like chess!)