Really late to the party on this one, but I'm am absolutely, 100% addicted to this game. It's available on both Steam and iOS/Android), and I'm playing the iOS version. It's stealing nearly all my gaming time from both the new FF XIV expansion and the FF XII HD remaster, something that I didn't think would be possible.
Having never played the physical game, I really had no idea what to expect. Tried it out on release, but the tutorial was SO bad, that I couldn't really make heads or tails of it. They patched in a better tutorial back in June, which has made a world of difference. It's not perfect, but at least got me to the point that I understand what the hell is going on.
At it's core, this is a card/dice game with fantasy tropes. You choose a party, explore locations, battle monsters, gain items, and level up. It's a very D&D'ish system, with each combat or action requiring a dice roll check against specific attributes. Characters have pluses or minuses to certain skills (i.e. a Wizard has pluses for high Int and minuses for low Dex, and vice versa for a Thief), and you can add blessings, allies, or items to dice rolls for a better chance of success. Hit points are actually determined by the number of cards in your hand and your deck, and management of this is absolutely critical. It's a very cool overall system that makes a ton of sense once you get past the initial learning curve.
I was initially very frustrated because of the time limit on each location, but once I figured out that both blessings and allies can be "spent" for additional turns, it solved most of that issue. It is still a dice-based game at heart, and RNGeesus can be incredibly cruel sometimes. It was apparently super buggy on release, but seems to be mostly stable now. The only bug I've run into is one that doesn't mark certain scenarios as complete. It doesn't stop progression, but can be annoying when trying to figure out which characters to bring along on specific quests in order to get the rewards (since you can only get them once).
My only real gripe is that while you do build a deck to some extent, you often are required to choose between multiple cards that you like, simply due to the small size of the card stash. If they doubled that, it'd be just about perfect.
I've dropped more $$ on this than any other mobile game I've ever played. Not because it's overly expensive, but because I enjoy it so much. On iOS, the first adventure is free, then you can pay $25 to unlock the remaining 6 (and all the characters), or buy them piecemeal. I payed the full fee, along with a few more $$ to get gold for treasure chests (additional abilities, spells, weapons, etc.). I don't think there's a free sample for Steam, but the entry price unlocks everything, iirc.