The chaos of love and marriage
This novel explains thematically that love is complicated, full of drama and betrayal, full of desire and disappointment. We see this in Megra's attempt to earn Pharamond from Arethusa (who doesn't even want to marry him anyway). Megra starts a rumor that Arethusa is sleeping with Bellario, but secretly Arethusa is in love with Philaster. You know who else is in love with Philaster? Bellario himself—or should we say, herself, because Bellario is Euphrasia in disguise. These clever, sometimes silly devices all serve to illustrate that love is like a chaotic dance.
Political life and fiefdom
The story is a lens into historical life in Europe, specifically in fuedal Sicily. Nothing could be a clearer picture of Sicilian medieval politics than for the novel to begin with a foreign king moving in and conquering someone else's castle. This kind of conflict between powerful lords is what defines Italian and Sicilian history.
Also, the sparing of a prince (for the preservation of hope among the newly conquered people) is a picture of the Machiavellian strategies that kings would employ. The other clear example of this is that the king tries to marry off his daughter for political gain (a very common practice, but also one that illustrates how obsessive these kings are with power; they're willing to sacrifice their own flesh and blood to gain a little more authority).
The catharsis of disappointment
The novel features a strange theme toward the end, as characters begin sorting themselves into couples and as the "chaotic dance" of courtship is coming to a close. As this happens, we find out that Bellario is a woman pretending to be a man. She has fallen in love with Philaster and has committed herself to being his page and servant, but in the end, when she does the big reveal, she still loses.
By having Bellario suffer disappointment with such deference, we see yet another theme—the catharsis of disappointment. The disappointment is cathartic, because at least she can drop the charade. In the end, she finds a way to be close to Philaster as his maid. In other words, she is defeated, but still in the game, still hopeful.
