How would you explain this sentence in the context?
On the streets you can see which men are farmers who’ve come to the city for the day: white trousers, rolled to the knees. The men taking coffee at La Flor were all black-trouser men. The ladies wore cloche hats and smart, short dresses like Mother’s, but with black stockings for modesty. The waitresses had white aprons and eyes wide with fright. This city is like Washington, and it isn’t. It’s difficult to remember real places from the book places.
PS: They(a boy and his mother) had moved from Washington to Mexico City the year before. And the boy read a lot of books.
How would you explain the last sentence: It’s difficult to remember real places from the book places?