As fiery a figure as John Brown was in American history, Ethan Hawke was surprised there hadn’t been more movies or TV series about him.

“This hasn’t been wildly overexploited,” he told reporters at the TV Critics Association press tour earlier this year. “There aren’t 15 John Brown movies we are talking about.”

That all changes in his surprisingly reverent adaptation of James McBride’s National Book Award-winning comic novel “The Good Lord Bird” (Showtime, 9 p.m.), in which Hawkes also plays the intense, bearded  abolitionist.

Being able “to reenact the raid at Harper’s Ferry and it has never been dramatized,” he says, “it’s so exciting.” 

But there’s far more to McBride’s sly story just before the Civil War.

“In the old days, when I would fall in love with a book, if you wanted to buy the rights to it, you knew you were going to have to throw 80 percent of the book away,” Hawke says.  “You were going to have to turn it into a two-hour movie, right? That’s just how cinema works. It’s haiku. And that was just the only way you would do it.”

Getting to tell a tale over eight hours on premium cable, “with the quality of artistry that’s happening,” it was possible to make a decent version of the book, he says. “We didn’t have to distill it to 20 percent of James’s book, and that is a huge.”