What is the theme in Paris to the Moon by Adam Gopnik?

The quality of loneliness preoccupied Gopnik in this book. Having come to a new place, leaving behind old associations with other people, he and Martha were more alone than ever before, and yet, Gopnik did not feel lonely. His little family was an island onto itself, but the principal reason for his lack of loneliness was a difference Gopnik perceived in how acquaintances interacted with one another in Paris compared to New York City. In Paris, shopkeepers, waiters, and others he encountered in everyday life constantly required bits of information about him. They wanted to know how he was going to cook the beef he had bought, or whether Martha was pregnant with a boy or girl.