The game has surprisingly little to do with Poker, in fact it’s just the hands that it takes from it (plus adding some of its own ones). It is basically a Solitaire deck builder. Apart from various introductions I’m sure you can find online, I can tell you the little stuff I know about the game in about an hour, though I only have about ~80 hrs in the game so far so there are most likely some better sources available.

The game can become very complex, but it’s not overly difficult to get into, and it’s very fun and well done. Not everything works on the higher difficulties though so there is some learning about how to approach the game.