(CNN) -- Comic book writer Harvey Pekar, the subject of the 2003 film "American Splendor," has died in Cleveland, Ohio. He was 70 years old.
Cuyahoga County Coroner's spokesman Powell Ceasar says Pekar was found in his Cleveland Heights home by his wife, Joyce Brabner, shortly before 1 a.m. Monday. The cause of death has not been determined and a full autopsy report could take several weeks, he said.
Pekar "was found motionless on the floor next to his bed," after his wife called authorities said Cleveland Heights Police Capt. Michael Cannon.
Pekar's wife told police that her husband was under the care of a doctor for prostate cancer and went to sleep in good spirits at 4:40 p.m. Sunday, Cannon said. There was nothing suspicious at the scene, he said.
Pekar was an acclaimed, underground comic book writer. He self-published his first edition of "American Splendor" is 1976. The comic series was a brutally honest look at his working-class life as a hospital clerk in Cleveland. The comic series had a cult following and was turned into a film in 2003 with Paul Giamatti playing Pekar. The film won the Grand Jury Prize at Sundance Film Festival.
In 1986, the New York Times Book Review said, "Mr. Pekar's work has been compared by literary critics to Chekhov's and Dostoevski's, and it's easy to see why." The review called him "a great storyteller with a keen eye and ear, an acute sense of ethnicity and a desire to make comics as esthetically rigorous and as rich in thought and feeling as the best literature."
Eric Reynolds of Fantagraphics Comics who met Pekar called him "a cranky man" who would be missed.
"For a guy who made a living complaining about life, he really did have a zest for it and it came through in his writing," Reynolds said. Pekar was a pioneer in autobiographic comics who "didn't shy away from revealing any of the nasty bits of his life. He didn't romanticize his life," he said.
Joseph Witek, an English professor at Stetson University, who got to know Pekar in the late '80s when writing "Comic Books as History," said Pekar was a sharp observer and critic of culture and society. "Pekar was the first autobiographic comic to concentrate on the everyday minutia of life and what it's like to get through a working day," Witek said, calling Pekar's writing style "warts and all" rather than "dark."
Witek said Pekar was a self-taught intellectual with only one year of college and called his death a great loss.
"There are many creators of autobiographic comics who are unaware of just how influential Pekar was and how indebted they are to him."
Dark Horse Comics, who published Pekar's comic series "American Splendor" from 1993 to 2003 posted a note on Twitter on Monday morning honoring his work: "We were proud to publish 'American Splendor' for nearly 10 years. Our hearts go out to his family and friends."