The Age of Jackson by Arthur M. Schlesinger focuses on the presidency of Andrew Jackson and its impact on American democracy and politics. The book first provides a brief biography of Jackson, describing his origins from a lower-class family in the West and his military successes. It then examines Jackson's administration in depth, analyzing how he expanded executive power and populism while also fostering the development of political parties. Overall, the work evaluates how Jackson left a lasting influence on the American political system during his transformative era as president.