The character of Charles Blenheim, in Jonathan Franzen's​ sprawling new novel, Purity, is a bright light of the literary world trying to write the big book that will earn him a place in the modern American canon. Once it had been suffice to write The Sound and the Fury and The Sun Also Rises, he complains. Now bigness, thickness, length were essential.

Franzen knows something about writing big books. He has written five novels of which The Corrections and Freedom are his most famous, two collections of essays and a personal history.

Purity, his new Great American novel, comes in a touch under 570 pages and there is little of the modern world that Franzen doesn't pick over - from greedy banks and feminism to the sad state of old-school journalism to the new freedom fighters of the Internet.

Charles wants to be Franzen but resents the type.

​''So many Jonathans," the pompous Charles complains. "A plague of literary Jonathans. If you read only the New York Times Book Review, you'd think it was the most common male name in America. Synonymous with talent, greatness. Ambition, vitality."

It's wicked and I say as much. "Maybe you can write an affidavit to that effect and send it to my publisher who wanted me to take it out," says Franzen by phone from his home in Santa Cruz. "And I almost did it because he is often right about these things but it was just too fun."

His gleeful self-mockery sits alongside the author's reputation for surliness and self importance. He's no friend of the internet and social media often rages about him.

Franzen, 56, has ticked off a number of female writers, who have variously accused him of either being backward in his commentary of women or failing to champion women's writing. Purity is unlikely to help his cause.

There was the public feud with Oprah Winfrey in 2001 when she uninvited Franzen from her book club after he said the schmaltzy novels she recommended were cringeworthy.

They've since made up but controversy tends to follow him. In recent weeks he caused a stir when he revealed  he had discussed with his partner of 18 years the idea of adopting an Iraqi orphan in part to help him understand young people better.

He can be intense, it is true, but what is often ignored is that amid the moralising and sharp observances, Franzen writes funny; not in a laugh out way but with angry bite in The Corrections, the book that made his name, and satirical levity in Purity.

"I think all of my novels are comic novels," says Franzen. "That's what comedy is for - slapping at the darkness. It doesn't have bite if it's not a little dark."

Purity follows squarely in the tradition of Freedom and The Corrections, but this is a book of broader international scope and topicality. There's a murder, and a suspenseful mystery surrounding the parentage of embittered 23-year-old university misfit Pip Tyler.

Tyler doesn't have a clue who her father is and, in pursuit of information about her real identity, accepts an internship with The Sunlight Project, an organisation run by the Julian Assange-like Andreas Wolf.

Midway through the novel, Franzen introduces the reader to online editor Tom Aberant and journalist/lover Leila Helou who bust open a story about missing nuclear warheads. Franzen holds a torch for boots-on-the ground journalism, a road not travelled. ''Of all the things about internet culture, the thing that makes me angriest is that it doesn't pay journalists," Franzen says.

Between Pip, Wolf and Aberant, Franzen sets up a discussion on the tyranny of the internet, and the narcissism of transparency advocates, comparing the likes of Google and Facebook to the cloak-and-dagger spies of the Stasi, from which Wolf is on the run.

Purity is both Pip's real name and the idea which carries Franzen's narrative from California to cold war Berlin to Bolivia, Wolf's headquarters of true believers.

"I thought about different kinds of idealists whether it was pirate party idealists, or young islamic suicide bombers or liberal language police, any number of  ... radical idealistic enterprises. They were all preoccupied in some way with purifying something, whether it is purifying language, or purifying religion or getting rid of money."

Simmering below the surface of this book lies Franzen's impatience with a generation that seems self involved and lacking his own youthful idealism. Franzen was ''angry politically'' and ''particularly idealistic about love".

"In a book about youthful idealism I think you see the idealism at work nowhere more clearly than when young people imagine they're going to have a perfect relationship; they are going to correct the mistakes their parents made, and they are going to share everything. I was in one of those and it's heaven for a while but it kind of turns into a hell because you lose yourself."

Franzen was born in Illinois  and  both The Corrections and Freedom are set in the American midwest with its white, small-town, conservative, middle-class values. The Lambert parents of The Corrections, are fictionalised versions of his own distant father and overprotective mother, both of whom are long dead.

This time, the flat floodplains of his childhood are not the centrepiece of his fiction. For Purity Franzen draws on his first ventures to live outside the ''American bubble''.

He went to Berlin on a Fulbright student scholarship in 1981. Too scared to speak imperfect German, he remembers his time in Berlin, and a longer stay in Munich, as isolating because he didn't make friends with local Germans. It was in Berlin that Franzen says he discovered Goethe and the modern German writers, and began writing his first novel.

For much of his early writing life, Franzen says he toiled in relative obscurity. His first two books, The Twenty-Seventh City and Strong Motion, were mostly well reviewed but not widely read. Mutual anxiety, ambition and competitiveness drew Franzen to David Wallace Foster and their friendship lasted until Foster Wallace's suicide in 2008.

By the time he wrote The Corrections in 2001, Franzen held a healthy "grudge against the world for not having recognised me as a writer". It's what makes The Corrections a much edgier, angrier book than Purity.

"A lot of the comedy is derived from a very angry writer, no question," says Franzen, who considers himself mellowed. "At the end of this book Pip looks at herself and she says, 'I've become a less angry person, and that's means I'm not as funny', and she recognises that it's her loss; she really loved being funny and I feel something of the same thing.

"I had to go for a different kind of humour in this book and it no longer consists of making fun of people's stupidity."

A book begins for Franzen with a proposal to his publisher.

"If you enjoy comedy you would enjoy reading proposals for the other two books," he says. "The Corrections was this proposal for a vast novel all about the American prison system. Freedom was a short comic novel about Republican party politics.

​"This was a little closer. I don't know why it happened but I actually wrote a book in some ways quite a bit like what I proposed, and I think that in some ways it was because this was so much more a plot driven book."

Franzen's love of bird watching dates to The Corrections, and the feeling for the first time he could relax and take some pleasure in life.  His love of nature gives rise, however, to another complaint about globalism: that the enormity of the world's necessary response to climate change paralyses local action.

One suspects Franzen prefers controversy to irrelevance. There can be nothing worse for his blood pressure, says the author, than to speak in a near empty hall. But celebrity has its pitfalls; people show up on his front doorstep all the time.

''I try to get rid of them, and they say, 'Do you want to have lunch?' and I say, 'No!'."

He was in San Francisco at a private dinner with his partner, whom he refers as his "spouse equivalent", when a reporter from BuzzFeed introduced herself.

"She practically held on to my arm because I had to participate in this amazing thing which she was experiencing, which was meeting someone she'd just been reading about."

Franzen repeats a line from Wolf where he describes fame as a lonely business. A few pages later Pip admonishes him for being self pitying. "I'm both her and him."

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