In order to assess how much is being retained, I like to always do some kind of hands-on craft/activity after we read a book to discuss the book & somehow bring the content to life. I like to see what my kids learned from the story, & hear about what they thought about it.
What was their favorite part? What character was acting silly? Was there something they didn't understand?
After we read the book, I Know an Old Lady Who Swallowed a Pie, we made our own "pumpkin pie" while we discussed all of the funny things that the Old Lady in the story ate.
This really was a super simple way to talk about the silly lady. We used construction paper, cotton balls, & plastic forks. Now that I think about it, I missed an opportunity here to talk about setting the table. Maybe next time hehe