the main problem I felt it lacked was that none of the characters were particularly likeable - it's very difficult to sustain interest in a book when you don't actually care what happens to anyone contained in it.
however as noted by the other reviewers, it gives you a remarkable sense of place, which is an amazing talent of Unsworth. His books are set in italy, in greece, on tiny islands in the Med, in turkey and each time you can imagine he must have a particular affinity with the place to portray it so well.
usually he just tends to like his characters a little more. which at least helps when the plot unravels hopelessly at the end you find you no longer really cared.