It’s a personality type familiar to many of us: the colleague who came in as your junior and just keeps getting promoted, despite being a complete and utter idiot; the highly caffeinated female boss who manages her team like a Serbian warlord, but thinks of herself as a really sweet person; the overly confident, sports-car-driving member of your social circle who has had sex with all the women and mocks all the men; and my recent pet hate, the skinny rich bitch at the gym who, when I said, “I’m sure these mirrors make you look fat”, came back with a haughty, “I’m sorry to say that no mirror ever lies, darling.” In case you hadn’t noticed, assholes are everywhere – and, what’s more, they’re doing really well on it.

The first line of Marty Kihn’s book, A$$hole: How I Got Rich and Happy by Not Giving a Shit About You, is: “I was the nicest guy in the world and it was killing me.” His wife, colleagues, boss and neighbour, the staff in his local coffee shop, the people he bumped into in parks, even his dog and cat – everyone was taking the P, according to Kihn, who works for a marketing company.

The final straw came when his boss told him that, unless he started playing hardball, they were going to demote him to a less aggressive part of the organisation – the humiliatingly termed “soft track” – and upgrade a colleague Kihn calls The Nemesis to a window office. Jung said that everyone has an opposite they want to be, a shadow self. In Kihn’s case, that opposite was an asshole. He decided to turn himself into one – and, in telling his story, he describes exactly how you can do it, too.

For all the inherent humour in his mission, the truth is, it really worked. By finding the balls to act like an asshole, he crushes The Nemesis, gets a promotion, then nets a bundle of cash, and a second home into the bargain, by selling the book to Hollywood for a six-figure sum – all this despite clearly being a big pussycat. “In corporate America,” he says, “if you are ambitious, or if you just want to go for the big money, it more than helps to be an asshole.”

Kihn built a serious team – acting coach, life coach and both personal and dog trainer – to help master the art of assholism. “You’ve got to try on a character for size,” he says. “The acting coach had me dress up in a bear suit, stand on Broadway and have people stare at me to remove self-consciousness.” This was just the start. He also stood in a mall, giving a dollar to anybody who would insult him, to try to stop caring what people thought. He practised aggressive sports such as boxing. He repeated asshole mantras and affirmations: “Clear your mind of all nice, helpful, self-defeating thoughts and replace them with mean, selfish, ass-kicking patterns.” Don’t pray to God, pray to a higher power in you, wishing every ill, including bad haircuts, on all your adversaries. The use of eye contact is also important. “If you stare at people hard enough, you can make them walk backwards,” he says. “I studied Al Pacino’s body language in Scarface: no smiling, his eye contact is constant. He doesn’t blink – Pacino’s eyeballs must have felt like sandpaper.” An asshole never listens to anybody. Tony Montana, from Scarface, and The Nemesis, from work, were his key role models. “A true asshole is someone who lacks empathy and has clear goals,” Kihn says. “Someone who unthinkingly takes credit for another person’s actions.”

He found inspiration everywhere he looked. He reels off some assholes: Donald Trump, Rudy Giuliani, Martha Stewart, David Letterman, the philosopher Ayn Rand – “The asshole’s philosopher, I call her. Any aspiring asshole could learn a lot from The Fountainhead or The Virtue of Selfishness.” Hollywood clearly is not short of A-holes, I say. “God, no. Nicole Kidman – I’ve been around her, observed her. I’ve never seen anybody with a more powerful sense of self.”

Throughout his experience, Kihn takes inspiration from many people, from Machiavelli (“It is necessary . . . to learn to be able not to be good”) to Paris Hilton, who hit the nail on the head with: “You should live every day as if it’s your birthday.”

Previously, Kihn was “like Hugh Grant in every film he made at the start of his career”. To me, he still seems incredibly, stutteringly, awkwardly nice, but, when I ask him to behave like an asshole, he switches it on immediately and convincingly: he looks away, bored, asks me to hurry up and get to the point, and checks his phone for messages while I talk. It’s an experience not dissimilar to interviewing your average Hollywood celebutante. It immediately shrivels my confidence.

The experience was “excruciating”, Kihn says. “It got easier, though. Practice makes perfect. I would not even have tried this experiment if I didn’t have the gift of desperation. I was so tired of doing what I was doing and getting what I was getting [which was not very much] that I was willing to put up with some pain. I had to consciously say ‘Your feelings don’t matter’, over and over, like a broken record.”

In the end, Kihn went back to his nice self: “I began to see the value in operating as a hybrid. People and relationships are more important to me than money and status.” His skills come out, though, every now and again, “usually when some fat idiot is blocking my way on the stairs”, he says, mimicking his shadow self. “But seriously, after I finished A$$hole, I left my firm and spent a year writing screenplays. Then there was the writer’s strike and my wife’s riding habit to pay for, and I found myself back at the old firm. They gave me an office without a window, so I used my technique of lying and taking the credit for everything, and very soon I had a nice window.

“Professionally, if I don’t need something from a person, I don’t even look at them. It saves a lot of time. It has affected my social life, too. If a so-called friend lets me down once, they’re off the list. And I never give my seat up on the train. It’s a long, weary ride downtown.”

Asshole: How I Got Rich and Happy by Not Giving a Shit About You by Martin Kihn (Penguin, £7.99)

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