Wild or comic, coupling in animals is quite frighteningly varied, and makes human sex look tame. Is that why most sex writing is so dull?

SEX; what is it good for? Is it, for instance, good for being written about? No other subject has people reaching for their dictionaries in quite the same way. There is pornography, there is eroticism, but is there anything else? D.H. Lawrence did it, Jilly Cooper does it, and everyone literary from Julian Barnes to Anne Michaels to Chloe Hooper does it; but have they actually written about it, or have they written about the stuff that surrounds it, the emotions, the personal politics, the sensuality, the awkwardness? Have they, in point of fact, in the main avoided the act itself?

A clue to writers' coyness might be contained in Olivia Judson's funny and blissfully original new book, which purports to be sex advice offered to the animal kingdom by a universal agony aunt called Dr Tatiana, and amply demonstrates the sheer unyielding ruthlessness of the business of procreation. Dr Tatiana has all the bossy heartiness of Bertie Wooster's Aunt Dahlia, but her science is first-rate. She responds with gusto to pleading letters from the Dandy on the Cowpat, a yellow dung-fly who wants to make his sperm more attractive, or Anxious in Amboseli, an African elephant who is diagnosed as possessing SINBAD (Single Income, No Babe, Absolutely Desperate). I-Like-'Em-Headless-in-Lisbon is a praying mantis who asks Dr Tatiana if she also enjoys the thrilling mid-sex spasms of a partner who has just been decapitated; and we are introduced to a female midge who plunges her proboscis into her mates' heads and turns their innards to a soup "which she slurps up, drinking until she's sucked him dry...only his manhood, which breaks off inside her, betrays the fact that this was no ordinary meal." There are several kinds of spiders, we learn further, "where there can be no doubting the females' intention to take head, not give it."

By contrast, Catherine Millet's explicit journal of unending sexual availability seems benign in the extreme. The book has been a bestseller in France and Germany, has received predictably prudish derision from British reviewers but is nevertheless prominent in the bookshops. Ms Millet herself is the editor of a French art journal, ART PRESS; apart from that, she has been enjoying orgies, open-air sex and indeed most conceivable kinds of sex for many years, and she has now kindly consented to tell us about it.

Her descriptions are laced with a laconic frankness which veers between intelligent reflection and willed self-objectification; the effect, if not the intention, is certainly pornographic. Her cool appraisals of looking for sex in the Bois de Boulogne are the essence of male sexual fantasy: she gives generously, and asks for nothing, a paradigm utterly foreign to the natural world described by Ms Judson. Ms Millet's book revels in its own sexual laisser-faire; like Tracy Emin's bed, it turns self-revelation into artistic statement. It is theatrical, but in the event limited to being a brilliant flourish. There are very few emotions other than frustration in the book, together with a weary avowal that she wishes it wasn't always her who was the first to get going at orgies.

Thank heaven, then, for Howard Jacobson; often criticised by the politically correct, he is able to milk the pain and humour of human sexual relations in a way that is part Tom Lehrer, part Woody Allen, part Thomas Hardy. He is underrated at home; in France he might be as celebrated as Michel Houellebecq, his writing recognised as of a stature to compare with Philip Roth's: dense, crafted and mature.

There are few writers who match sophistication and provocation in such a way: his latest novel, "Who's Sorry Now?", describes how Marvin Kreitman, the feisty but sordid luggage baron of south London, swaps partners with his friend Charlie, who is into nice sex and bored with it. Unlike Ms Judson's world of manic, ruthless and deadly copulation, or Ms Millet's one of vacuous self-abasement, Mr Jacobson's mockery of the way in which men are enslaved to their predilections is very funny, very painful and very human. In the end, the simplicity of the sexual clinch is a long way from the richness and absurdity of human desire. And not so interesting to write about.