With the Kisses of His Mouth, By Monique Roffey

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Just what the world needs: another sex memoir.

That is what we can all be forgiven for thinking when presented with the Orange prize nominee Monique Roffey's latest, whose jacket promises to be "provocative and explicitly candid" and to explore "hidden worlds". Surely we live in a post-Belle de Jour world by now?

Roffey certainly believes so; this is very much a companion piece, rather than a pale imitation. Devastated by the break-up of a six-year relationship – and particularly by her partner's shockingly thorough infidelity – Roffey chose to shun the vanilla politeness of most internet dating, and instead to plunge herself into a voyage of sexual discovery. Tired of boyfriends, she was hunting a lover. What begins with some tentative postings on craigslist.org ends as an international project taking in sex parties in France and Tantric workshops in Cuba.

Fans of sex memoirs will be reassured to hear that there are moments of startling candour throughout. But despite intimate descriptions of erotic massage classes and phone sex with strangers, there is less of Belle de Jour's lifestyle raunchiness and far more honesty about how sex feels – as opposed to how it looks. But at almost 500 pages, the book is considerably too large to be properly enjoyable. A gentle smirk at the dramatic change in Roffey's tone since her novel The White Woman on the Green Bicycle turns to a kind of resignation at the almost relentless descriptions of sex.

Consequently, where the book excels is also where it fails: it isn't convincing as a book about sex at all. Roffey's writing soars when she's describing the intense grief she experienced at the end of the great love affair that prompted her journey. Her knack of capturing the relationship's romance, even at its grimiest and most painful, is incomparable to the talk of the "grand changes" brought on by the innumerable tantric workshops she attends. Who knew so much intimate stroking could start to feel monotonous? By the time she is studying under the tutelage of a man named Harley SwiftDeer Reagan, the sexual discoveries are bordering on parody.

Yet Roffey is both wise and moving when examining her desire for romance; her propensity for creation myths in relationships; and how her ex "had a talent for love". And her flashes of humour are more engaging than the flashes of anything more saucy. Just as her tireless quest for self-improvement starts to read more like a tireless quest for further material, Roffey questions whether she is "author in search of a subject ... or ... furious horny bitch".

The answer is probably both and yet neither. What comes across most clearly is her desire to be truly loved. Roffey asks serious questions about what place sex has in modern relationships, and is blessed with admirable honesty. But if you're after lavish descriptions of exotic sex in exotic locations, you may be better served by a Jackie Collins novel. This is a surprisingly unsexy book.