There are themes, and then there are themes, in Italo Calvino's dense and fascinating book, Invisible Cities. It's possible to read this book on at least three levels. On one, there are themes like the nature of power; the cycle of life, death and rebirth; the illusion of happiness; and the power of language. On a second level, there's the theme of travel being the source of imagination and vice versa. On the third level is the theme of self-discovery.

Marco Polo tells tales of places he's been to the Great Khan, who at first takes them literally. Only later does he begin to suspect there's more to the stories, and the reader begins to do the same. The cities are dreams, or at least imagined landscapes, and recognizing this is the key to that third-level theme, self-discovery. If the tales are all imagined, they must tell us something about Marco Polo, which must tell us something about ourselves. Once we understand this, the purpose of the book becomes clear. It's a meditation on humanity. It's all there, parables about political power, warnings about the use and abuse of language, lessons about time and the raising up of awareness and social conscience.

The subordinate themes are building blocks. Marco Polo recites his poems in the same way students of religion or language chant, call, and repeat information to imprint it on their consciousness and to create a shared understanding of its meaning. The poems themselves are parables, like the fables used to teach children moral and historical lessons, or like the lessons one can learn from religious texts. They're all there because Polo, and through him Calvino, wants to teach us something. He wants to teach us the power of our spirits to shape the world, not in a religious sense, but in the sense that our will can create or destroy things if we want it to. We can make a better world, he's saying, if only we put our minds to it.

None of this emerges on the first reading of the book. You have to read it at least twice, read some criticism of it, and have a good long think about it in your own head, before a lot of this becomes clear. It's definitely a book to make you think.