Alan Gratz is a prolific writer of middle grade historical fiction. He grew up and lives in Tennessee. Many of his novels released to great acclaim, including Refugee (2017), which stayed on The New York Times Best Sellers list for four years. The novel follows three different children seeking refuge from various world conflicts, including World War II, communist Cuba, and the Syrian war. Gratz also wrote the historical fiction novel Grenade (2018), about two young men fighting in Japan during World War II. The men find themselves bonded to one another in the same way the characters in The Brooklyn Nine find themselves linked through a love of baseball and historical artifacts related to the sport.

In addition to Gratz’s historical fiction, additional works of his include titles about baseball. Samurai Shortstop combines a boy’s knowledge of baseball with that of being a warrior. Fantasy Baseball incorporates the world of fantasy with baseball, and The Brooklyn Nine tells the story of an immigrant to America and follows eight generations of his descendants.