The book 'A Letter to Thomas F. Bayard' is a scathing critique of the legislative power wielded by the United States Congress over the people of the country. Written by the American anarchist and abolitionist, Lysander Spooner, the book challenges the very foundation of the government's authority. Spooner was a well-known essayist, political philosopher, and legal theorist, who contributed to the development of both left-libertarian and right-libertarian political theory. He was a strong advocate of the labor movement and believed in anti-authoritarian and individualist anarchist views. Despite his libertarian socialist beliefs, Spooner also founded a company to compete with the Post Office. His works remain influential to this day in the fields of political philosophy and anarchist theory.