Write about what you know is the predictable advice given to budding authors. I think it’s safe to say that Ian McEwan knows more about writing and publishing houses than he does about spying and the MI5.
The acknowledgements are there to show that he did the required reading before putting pen to paper but anyone expecting some action packed James Bond style adventure will be seriously disappointed. The undercover role of agent Serena Plume doesn’t involve risking life and limb but winds up with her becoming a “writer’s moll” (with plenty of under covers work).
Her mission as a well-read reader of contemporary fiction is to recruit an up and coming writer named Tom Haley. The cunning plan is that his work can thereafter be used for propaganda purposes.
The author is in the dark about the MI5 involvement; he thinks he is being supported by a generous arts foundation. Sweet Tooth is mainly set in London and Brighton during the early 1970s. This means that McEwan doesn’t have to worry about the huge technological changes within security work. It allows him to concentrate on getting the period detail right through references to the provisional IRA, pub rock, the cold war, Edward Heath and the three-day week. He can also make quirky statements like: “Paper tissues were becoming ubiquitous, like supermarket trolleys. The world was starting to become seriously disposable”.
Serena is a prolific reader but doesn’t care much for ‘clever’ writers who play tricks on their readers (“I was the basest of readers. All I wanted was my own world and myself in it, given back to me in artful shapes and accessible form”). Haley has more of a literary taste; he likes poetry and experimental authors. He’s also a bit of new man who, in his stories “seems to know women from the inside”. He explains that fiction needs tricks if it is to work.
Of the novella that makes his name, he says: “The end is there in the beginning – there is no plot. It’s a meditation”. This is also a concise description of McEwan’s novel which begins: “My name is Serena Frome (rhymes with plume)and almost 40 years ago I was sent on a secret mission for the British security service. I didn’t return safely. Within 18 months I was sacked, having disgraced myself and ruined my lover, though he certainly had a hand in his own undoing”.
Having the central character as a sexy spy in her early 20s is a temporary distraction from the fact that the novel is essentially an autobiographical meditation on the world seen from a literary, rather than political, perspective.
There is a lot of stuff about the donkey work involved in writing and how the finished work then gets to be dissected by critics. There’s a cameo for Ian Hamilton of The New Review and knowing references to Martin Amis. McEwan seems to be treading water with this novel. It drifts along through some affectionate character studies but the lack of tension or intrigue means that it also ends up being smug, contrived and self-indulgent.
One of the characters in Sir Kazuo Ishiguro’s eighth novel says “It’s not faith you need. Only rationality.” Yet, while never undermining the importance of pure science, Ishiguro is primarily concerned with how humanity and machines can co-exist healthily.
With this novella’s strong focus on the burden of mortality and the melancholy reflections on ‘what-ifs’ from the past, it seems to me that, not for the first time, 
After her two previous bestsellers, Donna Tartt is in the enviable position of being able to call all the shots with any publisher.
