Few (including Lex Luthor) can match Robert Mayer's feat: killing Superman.

It was no easy task, by Mayer's account. In the early '70s, he abandoned his journalism career in New York City for a writing career in the City Different. In 1976, the unpublished novelist was in his late 30s. He hadn't read a comic book since he was 12, he says, but nonetheless penned 50 pages with this concept: "What if Superman were like a, you know, normal human being with these extra powers?" The first draft was called Clark Kent.

Comic enthusiasts and moviegoers these days are all too familiar with superheroes recast as flawed humans. Christopher Nolan's 2012 The Dark Knight Rises depicted Bruce Wayne as a washed-up recluse. In 2009, Director Zack Snyder gave Watchmen—Alan Moore's famous graphic novel depicting superheroes as flawed vigilantes—big-screen treatment.

This week, a new Superman movie, Man of Steel, hits theaters. It promises to delve into Clark Kent's origins, so it's a timely moment for comic enthusiasts to check out Mayer's Superfolks, which other writers have credited with pioneering the Superman-as-everyman motif that later inspired authors like Moore.

Mayer's own journey in part mirrors that of his newly fallible subject. In 1976, the president of Doubleday "loved it," Mayer says of his novel, but Mayer couldn't get copyright permission from Warner Bros. (According to Mayer, they feared the book would "destroy" Superman.) But Mayer skirted the copyright issues by renaming the book Superfolks, and he built a character who, at the beginning of the novel, is "losing his powers."

"He can't fly too good anymore," Mayer says. "His X-ray vision is sort of going off-kilter, and he's got all kinds of neuroses, including sexual ones. And the concept was in my mind: When we're 20 years old in real life, we're all immortal. By the time we reach our 40s—not so much anymore."

Mayer's book predates Moore's 1985 Watchmen and other "adult" comics. SFR asked him about his vision for how superheroes will evolve in the future, looking forward from the days of Ironman and The Dark Knight.

"I don't know, but the one thing I know is that they can never go back to the past," Mayer says. "Superman, he was like a grown up Boy Scout—and, well, in real life today, even the Boy Scouts are wrangling with these moral issues."