Alchemist James Reed attempts to create a human embodiment of the Doctrine of Ethos, a fundamental force of the universe.

In an interview with the Los Angeles Public Library, McGuire stated that Middlegame was inspired by the song Doctrine of Ethos by Dr. Mary Crowell.

[1] In an interview with Den of Geek, McGuire stated she was inspired by the Pythagorean philosophy idea that the universe is entirely made up of math and language.

[2] Paste called Middlegames "clever and imaginative", with "memorably menacing" antagonists, and compared it to the work of Lev Grossman.

"[4] Publishers Weekly lauded it as "genuinely innovative", "mesmerizing", and the work of "an author of consummate skill", emphasizing that the story's mutable timeline "demand(s) close attention from readers".

[5] Kirkus Reviews described it as "thrilling, emotionally resonant, and cerebral", and "Escape to Witch Mountain for grownups", but observed that "it isn't clear" how Reed's plan was intended to work, nor why his followers believe he would share power with them.

[6] Kirkus Reviews and Publishers Weekly included Middlegame on their list of the best science fiction and fantasy novels of 2019.

Middlegame, Seasonal Fears, Tidal Creatures, Ink Pot Gods, and an untitled fifth book would represent Fire, Earth, Water, Air, and Aether, respectively.