Some people think Robert Greene is evil. They’re the ones that read The 48 Laws of Power, his bestselling 1998 debut, saw the world depicted as a writhing snake pit of treachery and mind games, and felt that the author must be part of the problem. Other fans think he’s the solution, including Will Smith, American Apparel CEO Dov Charney (who calls it “the Bible for atheists”) and so many rappers, from Jay-Z on down, that the New Yorker dubbed him “hip-hop’s Machiavelli“. But when you advise your readers, “Discover each man’s thumbscrew” (Law 33) or “Pose as a friend, work as a spy” (Law 14), some are prone to expect the worst.

“I’m not who people expect me to be,” says Greene, an earnest, thoughtful 53-year-old with a somewhat tense smile. “I’m not Henry Kissinger.” In conversation at his London publisher’s office, as in his books, he always has an apt quotation to hand. “Charles de Gaulle said, I realised that when people met me they were expecting to meet Charles de Gaulle. I had to learn to be the man inside the quotes. But generally I prefer to be myself. I don’t have to pretend to be this mastermind.”

Greene doesn’t think he’s evil, obviously, but nor does he consider himself particularly good. He says he’s just a realist. “I believe I described a reality that no other book tried to describe,” he says. “I went to an extreme for literary purposes because I felt all the self-help books out there were so gooey and Pollyanna-ish and nauseating. It was making me angry.”

Even if The 48 Laws of Power can be read as a bastard’s handbook, he wrote it to demystify the dirty tricks of the executives he encountered during a dispiriting period as a Hollywood screenwriter. “I felt like a child exposing what the parents are up to and laughing at it,” he says. “Opening the curtain and letting people see the Wizard of Oz.”

Greene is accustomed to defending his first book, but I suspect he’s trying to move beyond it with his latest, Mastery, which studies how talent is developed, using a heavily researched slew of examples including Einstein, Darwin, Goethe and John Coltrane. “I was a little worried that young people would think the only game was being political and manipulative when really the bigger game is being so good at what you do that nobody can argue with your results,” he says.

Mastery is an illuminating book but its message (the secret of success is working incredibly hard for many years) is much tougher and more exacting than the follow-your-dreams manuals with which it will share the self-help shelves. “I hate them,” he says. “I was under a lot of pressure to write something faster and shorter and easier for people to consume and I resisted that. So maybe this book won’t sell because I’ve loaded the donkey with all that baggage, but I do at least try to debunk the idea that it’s all about your parents and education and wealth.”

On that subject, Greene himself had an “insanely middle-class” upbringing in Los Angeles. His father sold cleaning supplies while his mother was a housewife with thwarted artistic ambitions. After studying classics at college, Greene travelled around Europe, working dozens of menial jobs while trying to find the right outlet for his writing. Back in the US, he meandered through journalism and into Hollywood, before finally publishing The 48 Laws of Power in his late 30s.

His bestsellers (including the similarly gimlet-eyed The Art of Seduction and The 33 Strategies of War) have made him a wealthy man, but he could be even richer if he took all the offers that came his way. For one thing, he doesn’t think he’s a great public speaker. “I’m not like Malcolm Gladwell, who makes millions from that kind of thing. Maybe it’s a shortcoming. I’m so earnest in trying to give people so much information that I overdo it.” He laughs almost inaudibly. “I need to get a shtick.”

He turns down a lot of consultancy work because he is only drawn to people with interesting life stories, whether Charney (he’s on American Apparel’s board of directors), 50 Cent (they collaborated on 2009’s The 50th Law) or Barack Obama. He is now working with labour organisers in Latin America, and his liberal politics disappoint some of his fans in the business world, who expect him to be a champion of the ruthless go-getter.

“I’m a huge Obama supporter,” he says. “Romney is satan to me. The great thing about America is that you can come from the worst circumstances and become something remarkable. It’s Jay-Z and 50 Cent and Obama and my Jewish ancestors – that’s the America we want to celebrate. Not the vulture capitalist. These morons like Mitt Romney, they produce nothing. Republicans are feeding off fairytales and that’s what did them in this year and hopefully will keep doing them in for ever, because they’re a lot of scoundrels.”

Greene claims that most of the emails he receives are from readers who used his first book to understand and outwit manipulative people, but surely he has inadvertently created a few scoundrels himself? “There are people on the borderline and maybe the book helps them to move into that sociopathic realm so then I feel bad,” he concedes, “but mainly it’s positive.”

Mastery is so much warmer and more encouraging than its predecessors that I wonder if his view of human nature has softened. Instead of backstabbing brutes, are we in fact marvellous creatures?

He pulls a face, resisting the siren song of Pollyanna. “I’m not sure I’d go that far.