What are the best books about existentialism?

Some of the best books about existentialism include "Being and Nothingness" by Jean-Paul Sartre, "The Stranger" by Albert Camus, "Nausea" by Jean-Paul Sartre, and "The Myth of Sisyphus" by Albert Camus. These books explore themes of individual freedom, choice, and the meaning of existence in a complex and thought-provoking way.