Like a stoned Forrest Gump, Dennis Hopper always managed to be where the action was in American pop culture history.

When James Dean was inventing the Angry Young Man in "Rebel Without a Cause," Hopper was on the set (and in the movie).

When Andy Warhol was turning the art world on its ear, Hopper was buying one of his early soup cans (and went on to scoop up Rauschenbergs and Ruschas). When the old movie studio system was dying, Hopper used the success of "Easy Rider" to help drive a nail in the coffin.

Most of this he accomplished before 1970. Bedeviled by drugs and self-destruction, Hopper failed to live out a second act as fascinating as his first. Despite a few iconic roles in the ’70s and ’80s, Hopper accepted work in mediocre films (he was a long-tongued lizard king in "Super Mario Bros."), starred in some memorably bad ad campaigns and tried to cheat his colleagues from "Easy Rider" out of their shares of the proceeds.

It is this checkered persona that Cumming, Ga., native Tom Folsom illuminates in his biography, "Hopper: A Journey Into the American Dream." Folsom chooses a Kris Kristofferson epigram for his theme: "He’s a walkin’ contradiction, partly truth and partly fiction." Because Folsom, 38, cites no sources and opens with a fancifully constructed scene of Hopper riding a Harley to the promised land, it’s not always easy to tell the fiction from the truth.

We caught up with the University of Georgia graduate in his Manhattan home, as he prepared for a book launch party at the SoHo House in the city’s trendy Meatpacking District. Molly Ringwald was scheduled to appear, along with some "token Hell’s Angels."

Question: What made you want to write about Dennis Hopper?

Answer: The first time he ever got on my radar at all, I was a freshman at UGA, watching "Apocalypse Now," and he seemed so sort of dangerous in that role, it really stuck with me. It was the first time I remember seeing something that seemed more than acting, he was so intense on screen.

Q: This was a guy who broke his wife’s nose and tried to cheat his friends out of credit for his movie. Wasn’t he a pathological narcissist?

A: It was back and forth for me. As frustrating as he could be, he’d pull something off, that, wow, you’d fall in love with the guy.

Q: Why would he shill for Nike?

A: When he had an art collection that was worth millions? These were his friends; his art was his friends. He knew these guys too, he knew these artists. For him to pawn off one of his Warhols for some bucks, it wasn’t going to happen. It would be like cutting off a finger.

Q: He spent enormous effort on "The Last Movie," his follow-up to "Easy Rider," written by the author of "Rebel Without a Cause," and it failed. Why?

A: People thought of him as this countercultural icon. But there’s a big difference between making a film when you’re young and hungry and when you’re this iconic, almost prophet. He got caught up with that and his obsession. ... When you try and live your life as a movie, you’re going to get in that space between fantasy and reality and it is not a comfortable place to be in. There are going to be some extraordinary things in there and some despicable things, too. He had it both in him.