CLEVELAND – Harvey Pekar, whose autobiographical comic book series “American Splendor” portrayed his unglamorous life with bone-dry honesty and wit, was found dead at home early Monday, authorities said. He was 70.

The cause of death was unclear, and an autopsy was planned, officials said. Pekar had prostate cancer, asthma, high blood pressure and depression, said Michael Cannon, a police captain in suburban Cleveland Heights.

Officers were called to Pekar’s home by his wife about 1 a.m., Cannon said. He had gone to bed around 4:30 p.m. Sunday in good spirits, his wife told police.

Pekar took a radically different track from the superhero-laden comics that had dominated the industry. He instead specialized in the lives of ordinary people, chronicling his life as a file clerk in Cleveland and his relationship with his third wife, Joyce Brabner. His 1994 graphic novel, “Our Cancer Year,” detailed his battle with lymphoma.

The dreary cover scene shows him sprawled beside his wife on a snowy curbside with shopping bags on the ground. “Harvey, forget about the groceries, honey. Let’s get you inside first,” she says.

Pekar never drew himself but depended on collaborations with artists, most notably his friend R. Crumb, who helped illustrate the first issue of the ironically titled “American Splendor,” published in 1976. It was made into an acclaimed 2003 film starring Paul Giamatti as Pekar. The most recent “American Splendor” was released in 2008.

“Harvey was one of the most compassionate and empathetic human beings I’ve ever met,” Giamatti said. “He had a huge brain and an even bigger soul. And he was hilarious. He was a great artist, a true American poet, and there is no one to replace him.”

In 2003, the New York Film Critics Circle honored “American Splendor” as best first film for the directing-writing team of Shari Springer Berman and Robert Pulcini.

Part feature and part documentary, and with occasional animated elements, the film’s tearing down of the fourth wall — with Giamatti, as Pekar, often appearing alongside the real Pekar — paralleled his comic’s realism.

Pekar, himself, introduces the film and the character based on him: “This guy here, he’s our man, all grown up and going nowhere. Although he’s a pretty scholarly cat, he never got much of a formal education. For the most part, he’s lived in … neighborhoods, held … jobs and he’s now knee-deep into a disastrous second marriage. So if you’re the kind of person looking for romance or escapism or some fantasy figure to save the day, guess what? You’ve got the wrong movie.”

Pekar, who was a repeat TV guest of David Letterman, said in a 1997 interview that he was determined to keep writing his “American Splendor” series.

“There’s no end in sight for me. I want to continue to do it,” Pekar said. “It’s a continuing autobiography, a life’s work.”