Joyce has attempted it seems to me, with astonishing success to show how the screen of consciousness with its ever-shifting kaleidoscopic impressions carries, as it were on a plastic palimpsest, not only what is in the focus of each man's observation of the actual things about him, but also in a penumbral zone residua of past impressions, some recent and some drawn up by association from the domain of the subconscious. He shows how each of these impressions affects the life and behavior of the character which he is describing.
I've tried, at least five times to read the book... and failed each time. Then I tried the audiobook. Gave it up. I have to face it, I'm just not up to the task.