The Netflix show took its title from the first book in a trilogy, which is known as the "Shadow and Bone" trilogy. But half of the main characters in Netflix's series — Kaz, Inej, Jesper, Nina, and Matthias — never appear in that set of books.
Instead, they come from another of author Leigh Bardugo's book series: The "Six of Crows" duology.
Showrunner Eric Heisserer decided to combine the two stories into one new narrative, since "Six of Crows" is one of Bardugo's most popular books and it takes place in the same "Grishaverse" as Mal and Alina's story (just during a slightly later time period).
Heisserer said the first big challenge of making "Shadow and Bone" was figuring out how to put Kaz's crew into Mal and Alina's story with the Darkling.
"It was essentially inventing a prequel's worth of story for them and figuring out where they were at that time," Heisserer told Insider. "Since that was a few years before you see them in 'Six of Crows.'"
Insider also spoke with Bardugo, who says she had a lot of involvement during the beginning stages of the adaptation process.
"We've had long talks about how these stories fit together, because in my mind the show has become a kind of alternate timeline Grishaverse," Bardugo said. "It's not the way the stories play out in the books, but it absolutely could be."