Jeanette Winterson at The New Statesman:
Invisible Cities is built like a Boolean Truth Table. The mathematical table shows all possible combinations of inputs, and for each combination the output that the circuit will produce. It’s a logic operation. The categories we find in Invisible Cities – Hidden Cities, Cities and Desire, Cities and Memory, Thin Cities, Dead Cities, and so on – aren’t random. Once chosen, these “inputs” will reveal their “outputs”. Think of a Truth Table as including a column for each variable in the expression and a row for each possible combination of truth values (or cities in our case). Then add a column that shows the outcome of each set of values. That’s the dialogue between Marco Polo and Kublai Khan.
The mapping out of possible truth values is the hot debate sparred back and forth across the space the two men occupy whenever they meet. At first, Polo’s space is offered as places he has seen and been. Gradually, the emperor begins to describe the cities, and Polo must tell him if they are real – moving carefully around what the word “real” means.
Source: Italo Calvino’s Imaginary Worlds