Across the Green Grass Fields follows young Regan as she begins learning various truths about the world, including what it means to be a girl.

After her fight with Laura, Regan runs away from school down a path in the woods where she stumbles upon a door that she assumes must be part of an older student's art project.

[1][2] Kirkus indicated that the novella provides "probably the most literal iteration of McGuire's ongoing argument that biology is not destiny,"[1] a point Kristi Chadwick raised in her review for School Library Journal, as well, noting that "McGuire's inclusive characters are always presented fully formed and without cliché, and her critical takes on femininity in society are balanced with the beauty of the love of biological and found family.

Despite an overall mixed review, Grimdark's Elizabeth Tabler praised the book's "beautiful writing" with "a great explanation of centaurs’ matriarchal society, and touching descriptions of the real friendships Regan makes".

[4] On behalf of Library Journal, Kristi Chadwick similarly pointed to the "emotional and moving" prose, which she believes "will speak to the hearts and minds of readers".