THE IRONY IS, IT WAS ALL the wife's fault. She made him do it, because she was the one who wanted him to take the job in Shanghai. She was tired of being a mortgage slave and wanted a better life for their young daughter.

When they arrived in the Chinese boomtown, however, she was horrified by the squalor beneath the glitter. The baby girl she found in the dustbin was the deal-breaker, and she went home, leaving her hard-working husband all alone in a city heaving with sex. Seriously, can anyone blame him for screwing someone else? It was inevitable, really.

Tony Parsons describes My Favourite Wife as “a classic love story of the 21st century”. Well, it's not a classic love story of any century, though it's nicely written and highly entertaining. It appears, at first, to be something far more interesting. There are countless novels about infidelity from a female point of view. It is much harder, however, to find a novel that lays out the man's side of the story and explains the more puzzling aspects of his behaviour.

I don't want excuses; I want reasons. If the truth is that a husband has to be watched like a pan of milk, just come out and say it - the truth might not be noble, but at least wives will know not to leave him alone with the nanny (the use of the word “inevitable” in this context is particularly fascinating; if you leave me alone with your handbag, it won't be inevitable that I nick your purse). Are men's morals worse than women's, or just different?

The husband, Bill Holden, is a nice guy. He adores his beautiful wife, Becca, and their winsome daughter, Holly. When they arrive in Shanghai, they discover that they are living in a nialong - a birdcage - where rich old men keep their “Second Wives”.

One of these is a leggy beauty named JinJin. Bill fancies the pants off her. You know the rest. “Please come in,” she insisted, “I want you to try my dumplings.”

Bill falls in love with JinJin. Yet he still loves Becca. Can a man love two women honourably? Parsons bends over backwards to keep Bill clinging to the high moral ground - there's a rather silly rescue sequence near the end to show that both these women should be enormously grateful for even half his time. The fact remains, however, that he spends a large part of the book torn between two women, basically having his cake and eating it.

Why should a guy have to choose between sex and snuggles? It's heartbreaking that he can't have both. Eventually, feeling extremely virtuous, Bill makes his choice.

It is the stuff of many a male fantasy, and there is nothing wrong with fantasy. Parsons knows how to make you turn a page, and his evocation of modern China - “A medieval country with broadband” - is vivid and unsparing.

My Favourite Wife by Tony Parsons
HarperCollins, £17.99; 372pp

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