The book "The Unconstitutionality of Slavery" by Lysander Spooner is a legal treatise that analyzes the issue of the legality of slavery in the United States of America. Spooner convincingly argues that slavery violates basic principles enshrined in the Constitution, such as human rights, liberty, and equality. The author uses legal and moral arguments to justify his point of view and show the incompatibility of slavery with the principles of justice. This book became an important document in the struggle for the abolition of slavery in the United States and expanded the horizons of legal thinking in human rights cases.