A simple life. The egg & bird represent one's soul. The story is about one's soul maturing into a full-grown bird which resembles a Phoenix. The Phoenix symbolizes rebirth. So when your body perishes, your soul leaves the body and will be reborned. It's a little philosophical and abstract..
The aging Brother Aidan mentors the growing, young adolescent Brendan in the art of medieval Illumination; they make their home in various places throughout the Irish countryside as they are constantly evading the threat of the Northmen (Vikings).
In 'Kells,' The Secret Pleasures Of A Low-Tech Art