Based on the memoir of the journalist Toby Young, How to Lose Friends & Alienate People is the hilarious account of the fall and rise of Sidney Young (Simon Pegg), a hapless English hack on the make in New York’s media jungle. It’s a unique romantic comedy, for the real object of Sidney’s love is not the sexy starlet Sophie Maes (Megan Fox), nor even his sweet colleague Alison Olsen (Kirsten Dunst). No, he’s in love with a place: the magical kingdom of the famous that lies at the end of the red carpet, just beyond the velvet rope. As he puts it: “When I was a kid, I used to think there was a special place where all the movie stars lived, a kind of Shangri-la. And if you could just get inside there, you’d be happy for ever.”

I have to confess that I’m an old friend of Young’s, and when I first saw this film, I didn’t really enjoy it. But you know how it is with friends: you can be honest and tell each other the truth. So, when Toby asked me what I thought of the film, I plucked up the courage and did the thing we expect our friends to do: I lied and said it was really great.

Then, a few weeks later, I saw it again, and to my relief I really did think it was enjoyable. How come the change of heart? I didn't like the film because I loved the original book so much, and the film isn’t a faithful adaptation of the book. But why should it be? Once you forget the book, you can sit back and enjoy the fun.

When we first meet Sidney, he has found that Shangri-la in a star-studded film awards ceremony in LA. The film then flashes back a year to show us how he finally made it to the place of his dreams - and what causes him to wake up. Sidney is living in London, editing a small magazine, The PostModern Review. The film portrays Sidney’s staff as a bunch of unattractive, overweight, pretentious, pompous and infantile nerds. (As one of the unattractive, fat, pompous nerds who worked on Young’s magazine, The Modern Review, I must protest at this portrayal. We may have been a bunch of drug-fuelled dipsos, but the staff at The Modern Review staff were as good-looking, smart and talented as any magazine ever had.)

Anyway, while the staff are bickering, Sidney gets a call from Clayton Harding (Jeff Bridges), the editor of Sharps magazine, asking him to come and work for him in New York. For Sidney, it’s a dream come true.

By the end of day one in his new paradise, however, it’s clear Sidney is a fish out of water and starting to stink, at least socially. He loses potential friends on the staff and alienates the celebrities he’s meant to profile. At first, he relishes his role as the outsider who kicks the egos of the famous - but he ends up selling his soul to the queen of PR, Eleanor Johnson (Gillian Anderson), and starts kissing backsides instead.

The director Robert B Weide (best known for his work on Curb Your Enthusiasm) and the screen-writer Peter Straughan have made a film that occupies a place somewhere between The Devil Wears Prada and The Sweet Smell of Success. It’s a light comedy, but one that tackles the PR-driven corruption of contemporary magazines and makes serious points without delivering a sermon. In Sidney, we have a great antihero for our times, one who challenges, as well as embodies, the celebrity fixations of the age. He’s the little guy who says the unsayable and does the forbidden, the brash lad with cringeworthy chat-up lines and embarrassing dance routines. He is uncool and unPC, but a guy with a good heart.

Some will complain that the film isn’t as funny as the book. That may be true, but it has more laughs than any British comedy to appear over the past decade. Much of its comedy is rooted in slapstick and slipping on the banana skins of social norms and etiquette. Nobody does social embarrassment like Pegg, not even Hugh Grant. And nobody does the lovable loser with such conviction; that big babyface of his hooks your heart.

The film also reveals his talent for serious drama. When Sidney’s father (Bill Paterson), a philosopher, turns up at his son’s apartment, Sidney feels that he disapproves of his shallow life. You can see the terrible hurt across Pegg’s face.

We also get a wonderful performance from Bridges as the majestic grump Clayton Harding. There’s something touching about the relationship between the old editor and the brash young hack. Sidney may be Harding’s own pet monster, but he’s also a living reminder of the irreverent young man he used to be.

This isn’t a film about losing friends and alienating people. It’s about what happens when you lose your principles and become alienated from your better self.

15, 110 mins

Editor's choice

• The 100 Best Films of the Decade
• 70 facts you didn't know about Marvel
• The 50 Biggest Movies Of 2010