[2][3] King spent seven years as a counterterrorism operations officer for the CIA before quitting to write his debut novel, A Once Crowded Sky, after the birth of his first child.

[4][5] A Once Crowded Sky, King's debut superhero novel with comics pages illustrated by Tom Fowler, was published on July 10, 2012, by Touchstone, an imprint of Simon & Schuster, to positive reception.

[17] In San Diego Comic-Con 2015, Vertigo revealed a new creator-owned project written by King with art by Mitch Gerads titled The Sheriff of Baghdad.

[18] The project, a crime series in the vein of Vertigo titles like Preacher and Scalped, was set to launch in late 2015, and was inspired by King's time in Iraq as part of the CIA.

[24] As part of Marvel Comics' All-New, All-Different relaunch, King was announced as the writer of The Vision, a new ongoing following the titular character and his newly created family, with artist Gabriel Hernández Walta, colorist Jordie Bellaire, and covers by Mike del Mundo, launching in November 2015.

[25][26][27] The Vision has been well received by the public, with reviewers calling the series one of Marvel's "biggest surprises" and praising the narration, art, and colors.

[30] After negative fan response to the cancellation, Jim Lee, DC's co-publisher, announced that they would be bringing back The Omega Men through at least issue 12.

[31] Lee described the decision to cancel the series as "a bit hasty," crediting the book's critical acclaim and fan social media reactions as the reason the title would go on for the planned 12-issue run.

[36][37] King revealed via his Twitter account that he would stay on The Vision as writer through issue 12, finishing the story arc he had planned from the beginning.

[42] In June 2018 DC Comics announced King would be writing Heroes in Crisis, a limited series centering around a concept he introduced in Batman.

[45] In May and June 2019, King, DC Co-Publisher Jim Lee, and CW series actresses Nafessa Williams, Candice Patton, and Danielle Panabaker toured five U.S. military bases in Kuwait with the United Service Organizations (USO), where they visited the approximately 12,000 U.S. military personnel stationed in that country as part of DC's 80th anniversary of Batman celebration.

[46] In September 2020, DC Comics announced that King would be among the creators of a revived Batman: Black and White anthology series to debut on December 8, 2020.