Erotic abstinence is the potent subtext that sold more than 40 million copies of Stephenie Meyer’s young adult Twilight series, working like catnip on teenage girls, for whom the theme of forbidden sexuality holds particular resonance.

If you felt too old to read the books or see last year’s film, or if you were elbowed out of Waterstone’s ‘M’ section by a mob of ingénues, the four instalments feature Bella Swan, an ordinary high-school student, who falls in love with Edward Cullen, a teenage vampire who has sworn off human blood. The crux is that Edward must keep a tantalising distance from Bella to protect her from his blood lust.

The sizzling Edward/Bella dynamic is Meyer’s winning formula and abandoning it to write The Host, her first adult novel, would risk losing her marketplace monopoly on burning loins, along with the teenage characters to whom they belong. Perhaps for this reason, or perhaps in line with Meyer’s Mormon values, The Host seems constructed to preserve the sexual restraint of her characters Melanie Stryder and Jared Howe.

The narrative unfolds from the perspective of an alien, Wanderer, whose race of “souls” has enslaved humanity, inhabiting our bodies and going about our everyday lives slightly better than we did - like parasitic Stepford Wives. Melanie has escaped the aliens by hiding in the wilds with her younger brother Jamie and stealing food from houses. During a raid she runs into the rock hard abs of Jared, a fellow fugitive who says things like, “The thought of being separated from you…does it sound crazy to say that I’d rather die? Too melodramatic?” (Yes). But before the lovers can consummate their relationship, Melanie is captured in Chicago and Wanderer takes over her body. The host’s character is supposed to diminish, leaving only memories, but realising that her mind might lead the aliens to Jared and Jamie’s hideout, Melanie resists oblivion and ends up cerebral roommates with Wanderer, who eventually becomes her ally. Crucially when, in this state, Melanie is reunited with Jared, the pair cannot give in to their burning passion because it would amount to a threesome with an alien.

If this set-up is convoluted for sexual tension, Meyer has given the supporting edifice enough strength to make the endeavour more than tolerable. Her construction of the soul society is intricate and intriguing, she writes effectively on physical suffering (notably when Melanie and Wanderer almost die of thirst in an Arizona desert) and her narrative is compelling – like a post-apocalyptic soap-opera.

It is in fact Meyer’s trademark love story that lets her down. The host theme offers extensive opportunity for internal monologue and dialogue, which Meyer seizes to mar a perfectly good adventure. It might be unfair to criticise Twilight’s sprawling musings on love and lust, but The Host has been touted as an adult novel, so it is confounding that the internal life of her grown-up protagonist should read like the diary of a lovelorn fifteen-year-old.

Most irritatingly, Meyer sketches Melanie as a feisty, war-hardened heroin, and then shrivels her to a fawning waif in Jared’s presence: “Jared is magic. Jamie and I were perfectly safe while Jared’s instincts guided us; we never came close to getting caught. If it had been Jared in Chicago, I’m sure he would have made it out fine.” The last book to give me such a feminist prickle was by Enid Blyton.

This novel is a stranger hybrid than the dual being at its centre: an often visceral sci-fi romp encumbered with more saccharine than it can support. It is a pity that Meyer has kept one foot in the warm schmaltz of adolescent love, when she shows such promise as an adult author. As it is, her teenage fans will undoubtedly appreciate more of the spirit behind the Twilight saga, but the adults it purports to target would fare better with Jack Finney’s 1955 classic The Body Snatchers.

The Host by Stephenie Meyer is published by Sphere, price; £7.99

Explore Books

• Book Extracts

• Book Reviews

• Books Group

• Audio Books

Times Recommends

• Superfreakonomics by Steven D Levitt and Stephen J Dubner
• The Times picks the 50 best paperbacks of 2009
• Vincent van Gogh’s letters show the soul of the artist