Ilario is set in the same alternate history as Ash, about forty years before the events of that epic. It's a world in which the Visigothic city of Carthage is under the Penitence, an eternal darkness of unknown origin; in which Byzantium -- or rather Constantinople; that is to say, New Alexandria -- is the last stronghold, not of the Roman Empire but of the Pharaohs' Egypt; in which the Empty Chair in Rome is a symbol of the cursed papacy, and the schism of Christianity is between Christus Imperator and the Green Christ; in which Gaius Judas is a saint; a world which apparently revolves around Ilario, eponymous narrator of this novel.
I have written before about the difficulties faced by any reviewer tackling a novel narrated by a hermaphrodite. His? Hers? 'Its' is inelegant and, though it might feel right for a narrator who denies or is divorced from their sexuality, it's certainly not right for Ilario. Though the first five pages (which feature the only explicit sex scene in the novel) aren't representative, Ilario is seldom unaware of the sexual attraction -- and the uneasiness -- felt by those around him. Or her. [I'll end up using the male pronoun, I know I will: it carries less baggage in this setting, and I don't like the invented pronouns such as zir and hir.]
One of the major themes of the novel is appearance. Ilario, a painter by vocation who's desperate to learn the New Art of the Italians (perspective, painting only what one sees, et cetera), is well aware of how easily the eye is deceived: aware, too, of how much one can learn about something by looking at it properly. Truthfully. That perceptual laziness of the human brain, though, keeps Ilario alive more than once: people see what they expect to see, and if Ilario is dressed as a young woman then obviously the female pronoun -- and all it implies, in a society where women have no power, no legal existence, no rights -- is to be applied. And if some brawny fellow forgets that Ilario -- lately the King's Freak in the court of Rodrigo Sanguerra's court -- has been trained as a knight, well, it's his own fault if he picks a fight he can't win.
Another theme is the relationships between parents and children. Ilario is fleeing Rosamunda, who gave birth to the 'monster' twenty-five years ago, abandoned the child to die, and doesn't welcome the reappearance of Ilario in her life. Nor does her husband Videric -- who turns out not to be Ilario's father after all -- but he, at least, doesn't go after Ilario with a poisoned dagger. No: he sends Rosamunda to do his dirty work, stirring up some political difficulties that would better have been left to fester.
Ilario ends up on the run, a slave again, though this time his master, an Egyptian eunuch named Rekhmire', is less interested in his abnormalities than his talents. He encounters his father (by far the most likeable character in the novel); gets married; gets married again, on the other side of the bride/groom divide; meets the 'Master of Mainz', a German gentleman with a newfangled invention that'll make seditious publication ever so much easier; encounters Neferet, Egyptian Ambassador and not what she seems; meets the Pharaoh, who only wears a beard for formal occasions; sketches the biggest ship in the world, and its Admiral (who is rather badly lost); and finally achieves a penitence of his own, in a cause that practically everyone (including the reader) notices before Ilario does.
I liked this much more than I liked Ash: possibly it's the focus on arts and science, rather than on matters martial; perhaps a more likeable protagonist (though Ilario exhibits poor impulse control pretty much constantly, and behaves more rashly than a protagonist in a Shakespearean comedy); perhaps because I recognise many more of the historical and ahistorical references now; perhaps because the story feels more rounded, more concluded. And it is a story that depends on its protagonist's dual nature:
If I were a man, I wouldn't know what goes on in the Ladies' Court, and if I were a woman, I wouldn't have any different experiences to make the comparison.