I interviewed Alexander McCall Smith for the Literary Review last year, when his books about the No 1 Ladies’ Detective Agency had suddenly become worldwide bestsellers, and The Sunday Philosophy Club was just out. He said he was trying to make up his mind about its sequel: was its heroine to have an affair with the delightful Jamie? Isabel Dalhousie is an Edinburgh worthy, in some ways a chilly northern equivalent of the delightfully extrovert Botswanan Mma Ramotswe. Both are middle-aged women who take a more than neighbourly interest in other people’s business. In Friends, Lovers, Chocolate, Isabel develops more than friendly emotions towards a much younger man. Jamie is the ex-boyfriend of her niece Cat, Isabel is an unmarried philosopher who has been single since her heart was broken by an unfaithful Irish philanderer. She has limited experience of the world, living on inherited money in her childhood home, looked after by a fierce but faithful housekeeper, and her knowledge of human emotions, her own or anyone else's, is more theoretical than practical; but she is immensely erudite, relentlessly analytical, and a decisive editor of The Review of Applied Ethics. Reviewing a book called In Praise of Sin or rejecting an article on 'The Rightness of Vice' is easier than understanding the customers she meets in Cat's delicatessen.

One is a distressed stranger who presents her with an interesting idea: is it physically or philosophically possible that a transplanted organ might have given its recipient not only life but also the donor's memories? Isabel picks up the problem and runs with it, blundering into other people's privacies with