Every book is partly a puzzle to be assembled, a labyrinth to be explored by its reader, a repository of buried secrets waiting to be unearthed. No surprise that the mystery genre, in all its permutations, is so enduringly beloved, because it is in the nature of all readers to enjoy ferreting out concealed treasures and discovering secrets perhaps known only to themselves. Every city has similar hidden delights, and true city-lovers never tire of ferreting out the mysteries of their metropolis.