When a video goes viral on the internet, you might expect it to feature a kitten dancing on a hippo, or Russell Brand telling an awards ceremony about breasts. Not a theologian putting a Fox News interviewer bang to rights on why he, a Muslim, had dared to write a book about Jesus. Yet a clip of Reza Aslan doing just that went viral this month, pushing his book to the top of bestseller lists.

"Just to be clear, this is not some attack on Christianity," he said of Zealot, a book describing Jesus of Nazareth as an illiterate, trouble-making social revolutionary (and a very inspirational one at that), to an anchor who could not get past his suspicious Muslimness. "My mother is a Christian, my wife is a Christian, my brother-in-law is an evangelical pastor." The anchor was undeterred, determined to reveal a secret Muslim agenda. "My job as a scholar of religions with a PhD in the subject is to write about religions," he insisted. The clip was watched and cheered by millions – it was extraordinary.

But then, as I discover when I arrive at Aslan's home in Los Angeles to interview him, the Iranian-American's life as an academic is already extraordinary. For a start, there's the Hollywood Hills location, not generally associated with Bible scholars. There's the smoothness of his manner when he enters the room, passing a Banksy book displayed on a miniature easel in his living room, flashing me a dazzling smile as he pats the family poodle, embraces his twin toddlers, "My beautiful boys!", and tells his wife he loves her. Twice.

He runs a production company that develops content about the Middle East, is a consultant for movies, and appears on The Daily Show and The Colbert Report. He's merrily compiling a folder of emailed death threats and people are hounding his wife to ask if Aslan beats her and forces her to wear a burqa. (She's looking immensely cheerful in a tracksuit.) When I point out that the Fox hoo-hah must have been great publicity for his book, he agrees, but gently reminds me that it was already at number three.

"The number-one cable news show in this country is Bill O'Reilly – but he only gets one million viewers – there are 350 million of us. So the idea that Fox News drives the public conversation in the US is absurd, and yet even our politicians – even our president – buy into that." Does the fact that people believe it make him want to lob a brick into the telly? "Sure – but you've got to pick your battles. You're not going to win the battle against Fox News – but only because they're not interested in the war."

He sounds like a character from a David Lodge novel – the controversial academic who has recast himself as a self-assured Hollywood dude on a mission to bridge the gap between ivory towers and the real world.

"There are times when I'm invited to dinners or parties at celebrities' homes – no I don't want to name names," he says, apparently embarrassed but obviously loving it, "and I'm like: 'Ooh, all these cool celebrities!' But nobody wants to talk to anybody but me. In LA, the celebrities view the intellectuals as the celebrities."

Aslan was born to ostensibly Muslim parents in Tehran in 1972 and fled to the US with his family seven years later when the revolution removed the Shah from power. They lived a fairly secular life and he had no religious instruction as a child. Yet he was gripped by religion, eventually attending Harvard Divinity School and holding various teaching posts. He sees himself first and foremost as a storyteller, and is associate professor of creative writing at University of California, Riverside.

"I only write so much about Muslim issues because Islam pays the bills," he says smiling. Some reviewers have criticised Zealot for being too populist, but Aslan says that was the point. It was written to be a page-turner, full of cliffhangers and provocative explanations of Jesus's metaphors. Plus, of course, the bit about how as a Jew, Jesus was "exclusively concerned with the fate of his fellow Jews".

The morning we meet, Richard Dawkins has tweeted a suggestion that Muslims haven't achieved much of note since the Middle Ages. "I'm not interested in Richard Dawkins," says Aslan who hadn't seen the tweet – possibly because he was busy retweeting all the death threats he receives. "I find him to be a buffoon, embarrassing himself every day. This is a guy who said: 'I've never read the Qur'an', but often says that Islam is the greatest force of evil in the world. He's the worst kind of zealot."

Aslan became an evangelical Christian in his teens, but his faith severed at college, partly after reading The Brothers Karamazov. "Jesus and I are like a married couple that are divorced but will always be friends – more than friends." He is a man of faith, but says: "You can't spend your life studying the world's religions and take any one of those religions all that seriously, in so far as it's a manmade set of doctrines espoused and enforced by an institution. I self-identify as a Muslim now because the language of it makes most sense to me."

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