You dare not give them your confidence, particularly as even they seem unsure of themselves. The identity of the audience is unclear. These are characters whose very blood carries not oxygen, but ambiguity. Perhaps their statements are directed towards the author Jeanette Winterson, to each other, or even to themselves. To believe that the reader is being addressed directly is pure vanity.
Uncertain narration is usually present in novels, even if unstated.
Here it is more vital. Like the physical city of Venice, the narrators are trapped in a mental landscape whose streets change as they walk down them. The mental landscapes may even lead beyond the city itself, to an island Necropolis perhaps, where the dead call upon the living. Or, worse, one might walk into the hidden city, where the living call upon the forgotten and both will soon be dead. The only way to keep track of such a city, to keep from allowing it to master one completely, is to keep notes.