Bartholomew, an intelligent iguana with brown-and-green mottled, scaly skin, loves riding the New York City subway. The underground railroad, which clatters and whooshes before it takes off, teems with people, but Bartholomew doesn't mind. He enjoys his escape from his life in a museum exhibit and spends the morning observing other passengers.

On his ride, Bartholomew watches several Regulars and learns about their similarities, their differences, and how they interact or don't interact with others. Bubbly Becky radiates joy, and she even sits next to Bartholomew. Fred always wears a bright scarf and sometimes hums, but he keeps to himself. Mrs. Hatmer keeps her four children organized, but some passengers are annoyed by the kids. By the end of Bartholomew's ride, he learns about the value and uniqueness of each person.

Bartholomew, Squire of the Subway includes questions in the back to encourage young readers to explore the lessons Bartholomew learns. Carol Lester's children's books spark discussions with adult and school-aged readers alike. With each book, Lester seeks to influence and shape lives, young and old.