What are some story excursions in Exodus chapters 19 and 20.

I'm not sure exactly what you're looking for. These two chapters are about God appearing to Moses and the Israelites, the Israelites' fear of seeing God, and some of God's commandments to the people, including the 10 commandments.

If you're looking for a good resource on Exodus, Fretheim's commentary on Exodus is wonderful.

I would also like to point out a neat tidbit I picked up in a college class on Exodus about this passage. When the passage says that God carried them on "eagle's wings", the original text actually says "vulture's wings". The translators just changed it because they didn't want that image in the book. Apparently, vultures aren't good enough. Haha.