Seanan McGuire's 2016 novella Every Heart a Doorway was a mean, beautiful, hopeful fairy tale about a boarding school for kids who once opened a door into a magical world, only to return to mundane our earth broken and sorrowing. In Down Among the Sticks and Bones, a prequel published today, McGuire sharpens the tip of her literary spear to a lethal point, telling the tale of Jacqueline and Jillian, twins who opened a door and found themselves upon a moor where they were apprenticed to a vampire and a mad scientist.

Down Among the Sticks and Bones plays to McGuire's strengths, her ability to write matter-of-factly about gender and identity without losing sight of the pain that precedes the joyous release of realizing who you are, separate from the constraints of society's expectations. Jacqueline (Jack) is raised to be a girl's girl in princess taffeta, punished and shamed any time she gets dirt on her hands, while Jillian is raised to be a tomboy, short-haired and trousered and constantly sweaty and exhausted from soccer practice.

The twins' parents see them as ornaments and marionettes through whom they can enact their fantasies of perfect domestic life. Their grandmother — the only person to accept them as they are and treat them as humans in their own right — is sent away in the dead of night when the girls are but five, leaving them without a shred of trust in adults around them, making them especially vulnerable to what they find on the other side of their magic door.

Jack and Jill grow apart, pushed apart by cruel manipulation and expectations. But one rainy day, when Jacqueline has no books to read and Jillian can't go outside to play sports, they happen upon their grandmother's old dress-up trunk in the attic, long forgotten and full of promise. Opening the lid reveals an infinite staircase spiraling every downward — and not the pieces of old costumes they fondly, albeit dimly, remembered.

Down and down they go, emerging upon a moor, or rather, a Moor, a brooding, sinister place where werewolves rule the woods, unspeakable elder gods demand tribute from the sea, a mad scientist does unspeakable things in the windmill — and a vampire rules over all from his castle.

Finding themselves wards of the vampire, the girls face a choice: remain with him as vampire princesses, ruthless and elegant; or be apprenticed to the mad scientist and plumb the unplumbable mysteries of the universe, of life and death and all beyond.

Here's where McGuire shines, in showing how Jillian — not the feminized Jacqueline — discovers a secret yearning to be treated as a princess (perhaps because, having been treated as a tomboy all her life, she fails to grasp the cost of such a role); while Jacqueline, in her frilly dresses and all, decides that being a jewel in someone else's crown is no life for her. The two girls part ways, and become new people altogether.

Jack and Jill's story twines their genders, their identities, and the resilience and failings of each, around a sing-song fairytale that is deceptively simple and soft-edged, and whose calm surface hides deep thorns that will snag at you and draw little pricks of blood. McGuire's at her slyest and canniest here, making the very difficult seem easy in the manner of Rogers and Astaire. Let us all hope there will be much more to come in this vein.

Down Among the Sticks and Bones [Seanan McGuire/Tor Books]