"Beauty is frequently boring. The nose of a human Barbie can only be so long, but there is an infinity of deformation," Eco said of the subject he tackles in "On Ugliness", his latest work which he presented here.
He said ugliness represents a "moral battle" and its varying definitions lay bare class differences.
The book, which is illustrated with portraits by painters throughout the centuries, was released in Italy last week and is a follow-up to his 2005 hit "History of Beauty", which sold half a million copies in 27 languages.
Eco, who is best known for "The Name of the Rose", said he also found ugliness far less distracting to write about.
"I was not disturbed by sexual desires."
Ultimately he believes that grace might be the most challenging topic.
"Barbra Streisand and Gerard Depardieu have it -- they are not beautiful -- but what is it?" he asked.
This also served to prove again that between beauty and ugliness lies a big grey area, the bearded author said.
"The world cannot be divided into beauty and ugliness -- in between there is me, for example."
Eco was seen as having an outside chance to win the Nobel Literature Prize on Thursday, but it went to British author Doris Lessing.

Copyright AFP (Agence France-Presse), 2007