Shannon is still working in the fantasy realm here, but she created a whole new world to set this series in, and based on this first book, she's done a pretty good job. It seems clear from The Bone Season and now this book, that for Shannon, inclusivity and equality are fundamental. Its a good place to be, but how she's done it in this book is to bake it right into the world she's created. Its just normal, and anyone who feels differently is the outsider. Its an effective tool and reminds me a little of Ursula K. Le Guin.
You can tell by the cover art that there be dragons here, but Shannon has them with a different take. In the front matter, the book jacket, somewhere there is a note that the fictional lands of The Priory were inspired by legends from various parts of the world. or something like that Shannon has taken a kit of parts provided by various myths and legends around the world and reformed them into a massive crossover that forms the basis of her world building cultures, economies, magic, and religions. Its because they are familiar, that she can lean on them to help infill the backstory. The same technique is used for place names and personal names, which are similar to those cultures that inspire them, but different enough to set them apart. Western Dragons, with the wings and fire, are set against the Eastern Dragons, which slither through the air and and more water based.
This book is a beast at nearly 850 pages, and traverses the globe Shannon has created, following the stories of people from several different countries, who eventually learn that they probably need to work together to defeat an insurmountable common foe. I didn't love this book, but I did like it. Enough to go to the library and get the next installment, A Day of Fallen Night, which, so far at least (its another big one) is a prequel to The Priory.