the world in this book is a sort of alternate-universe Transylvania underneath your “real” Transylvania, reachable through mirrors
A close inspection of the map, however, reveals a land far larger than Transylvania, with Cachtice in the north-western corner, Zombor in the south-west, and Castle Poenari in the south-eastern corner. The north-eastern part of the map is more difficult to identify with any real-world place names, but the shape of the rivers and of the mountains suggests Ruthenia.
As a result, given these geographical limits, the Land of Unreason corresponds quite exactly to the historical Kingdom of Hungary, i.e., the model behind my very own “Fair Kingdom”.
The Land of Unreason used to be a unitary kingdom, the Once Palace. After the demise of the latter, it became a war-torn land, with the two main powers being the Heart Queen, based in the north-west, and the Red King in the south-east. This again somehow reflects the disunity of the Fair Kingdom, torn between the Empire of the One Faith, the Empire of the Crescent Moon, and the independent-minded nobles of Transylvania, who try to keep their distances from both empires.
Should you want to run a mash-up of my Fair Kingdom setting, with its icons, and the Land of Unreason, you could expand on the notion of Twins presented on page 16 of A Red & Pleasant Land. The Fair Kingdom is the geographical twin of the Land of Unreason (and vice-versa). Everybody has a twin in the other land (and vice-versa). The Heart Queen is the Twin of the Blood Countess. The Red King is Vlad Dracul's Twin.