In 'Purity', novelist Jonathan Franzen tackles the web's propensity for mob justice

Jonathan Franzen's latest novel, , is partly set in Santa Cruz, a California town 100km south of San Francisco, where the novelist lives with his partner. Their house is in the U-bend of a crescent, on the edge of a suburban housing estate, overlooking a wooded conservation area to the Pacific Ocean beyond.

It is, for one of America's foremost literary novelists, a modest property, overlooked on three sides by neighbours in a way that, say, Philip Roth's estate in Connecticut is not. However, it affords good views from the deck (the novelist is an avid birdwatcher), and the low overheads permit Franzen to let five years go by without delivering a novel.

"I'm not used to talking about this book," he says of , which, like his preceding two novels, is a 600-page doorstopper. There is a long, Franzenian pause: "I'm trying to figure out how much I should say and how much I should not say."

That question, as central to the writing as to the publicising of the novel, is one that Franzen has frequently struggled to answer. At 56, he has the earnest, slightly puggish look of a younger man, and the occasional intemperance of one, too. His fame has as much to do with the fights he has picked - or has had foisted upon him - as with the quality of his fiction; Franzen riles people in a way that is unusual, and perhaps reassuring for a novelist, given the endless debate about the relevance of that role. He has attracted the scorn, over the years, of users of social media, environmentalists, certain stripes of feminist critic, lesser novelists, the lead book reviewer of and fans of Oprah Winfrey.

Franzen says he is "hurt" and "ashamed" to be the target of such ire, but he is also unrepentant. No sooner has one controversy died down than another pops up in its place, most recently in the wake of a long piece he wrote in in April, suggesting that, contrary to research published by the bird charity the National Audubon Society, climate change is not the greatest threat to avian welfare, but more immediate dangers such as hunting and collision with glass. The society accused him of "intellectual dishonesty", and its members attacked him online, an unpleasant but also, perhaps, a bleakly satisfying experience: the incident foreshadowed the themes of Franzen's new novel.