Venice as a metaphor for time
Venice is a metaphor for time for a few reasons. The setting of Venice has strong imagery associations to Italy's rich cultural history since the buildings there are often very old, and because Venice also bears a curse of doom; it is likely to flood. That makes it a natural symbol for time in this book because the question of Italian floods is a natural analog for the original flood story, the epic world flood described in Genesis 3. Venice is the whole world, and the flood is a metaphor for time's power to erase humanity from the earth. What survives such a flood? Stories, and that's why the women tell stories in the ark.
The Biblical allusion
The Biblical allusion of the novel constitutes the majority of its plot, because outside the meta-narrative provided by such a strong allusion to Noah's ark, the book is largely unguided reflections on a woman's daily life in Venice. The major plot of the book is assumed from Noah's well-known tale of survival and obedience. Remember also that the story of Noah is proto-historical; even when it was written in the far ancient past, it was already considered to be an ancient story. The allusion is therefore also a suitable consideration on time, because modern Venice is compared to a time before written language.
The role reversal
The role reversal of the title is a promise well-kept by the novel's substance. As the reader continues to remember the story of Noah, the writer weaves in wrong notes that are sure to gather attention. For instance, when the woman commits the acts of God which lead to salvation, she places herself in the role of hero and prophet (because Noah is a proto-type for the savior motif). Then, compare her success to Noah's; Noah was able to build the ark and save those under his control, but those outside his domain were not convinced. Mrs. Noah is clearly more skillful with social situations; she was able to save a quite pleasant group of women who spent their flood telling stories.
The sibyls
The sibyls offer the whole of the narrative, but through five separate lenses for a complicated comparison and contrast. This is one narrative feel, but broken into several dominant and sub-dominant sections of prose for a symphonic effect. The sibyls are like prophetic interpreters who derive from ordinary nature epic lessons for the soul, and their subject material is the protagonist's simple life, which they see as a continuation of epic themes from eternal times past and future. They are symbols for the epic quality of the human experience, similar in function to the fates, the furies, and the choir from Greek tragedy.
Realism and mythology
The convergence of Greek themes about heroism and story-telling (the sibyls are part of Greek tradition, more or less) and Jewish themes makes this novel an eligible candidate for the title of "epic" literature, because although the novel plays on those influences, it is clearly also derived from those influences. The cultural expression of those influences can be found in the motif between the realism of the protagonist's life and the juxtaposition of that realism to the mythic language of the sibyls. The question is whether a normal human life constitutes the height of heroism that is found in the ancient past, and the book seems to be saying, "Yes, it does."
