Richard B. Woodward in The Village Voice:
Umberto Eco is 75 and has entered the autumnal stage of intellectual renown when publishers sell his books with his name rather than his actual writing. He is not yet the factory of anthologies that Harold Bloom has become. But like On Beauty, Eco’s previous well-packaged venture into aesthetics, much of On Ugliness is a collection of quotes from writers— Aristotle, Dante, Milton, Kafka, Sartre—who are even bigger brands than he is.
As a historical survey of our responses to horror, this format is fine so long as you don’t expect the semiotician-cum-novelist to spend much time analyzing these matters. The muddled relationships between ugliness and evil, physical and moral deformity, dread and mockery of ugliness he’s content to leave muddled, pointing out simply their conjoined ancestry.
Eco starts off with a few promising insights.