I have not gotten that far into it, but from what I have seen it is not a run-based deckbuilder like Slay the Spire or Monster Train where you start fresh each play session with a set of basic cards and add to it from there, but I think it counts. Each character (you start with one, but there are obviously more) has a basic deck of cards (“pages”) that are (at minimum, remember I only have one character so far) attacks of the various elemental types. You and the enemy take turns playing these (there is an initiative roll every turn), and when you beat enemies they turn into books that seem to be involved in summoning new enemies to fight, but you can also burn the books to get more “pages,” some of which are moves that can go into characters’ decks and some of which are character equipment.