I will try to help you by answering by heart, I will think of 5 (not 20, seems too much) moments in the book I really liked - :
1. at the beginning, a passage which explains that living in Brooklyn was a choice of inner retreat
2. Passage about daughter, where he says he doesn't think his daughter is a very interesting person.
3. When he discovers his nephew in the bookstore, about the coincidence that whenever he came in, the nephew was upstairs, except for that one time.
4. The description of the fat queeny lovable crook who owns the bookstore.
5. The passage when he proposes to Joyce's mother (what was her name? anyway the mother whose pretty daughter had a husband named jimmy joyce)when he proposes and she refuses by weeping so touched she is by his effort to conform to expectations, despite his total inability to have ever done so.