In the hands of many of the great writers, the unravelling of mystery is only one strand within a complex project. Other things get unravelled, too - the belief in a rationally explicable world, in the beneficent, ordering force of culture and civilization. Constantly the detective story delights in muddying the waters, in acknowledging the omnipresent possibilities of anarchy and carnage. As a genre, it is supremely able to combine popular appeal...