The delightful second installment in Alexander McCall Smith's already hugely popular new detective series, The Sunday Philosophy Club, starring the irrepressibly curious Isabel Dalhousie -- editor of the ''Journal of Applied Ethics'' -- and her no-nonsense housekeeper, Grace. When Isabel's niece, Cat, asks Isabel to run her delicatessen while she attends a wedding in Italy, Isabel meets a man with a most interesting problem. He recently had a heart transplant, and is suddenly plagued with memories of events that never happened to him. The situation appeals to Isabel as a philosophical question. Is the heart truly the seat of the soul? And it piques her insatiable curiosity: could the memories be connected with the donor's demise? Grace, of course, thinks it is none of Isabel's business. Add to the mix the lothario Cat brings home from the wedding in Italy, who, in accordance with all that Isabel knows about lotharios, shouldn't be trusted . . . but goodness, he is charming. That makes two mysteries of the heart to be solved -- just the thing for Isabel Dalhousie. ''From the Hardcover edition.''