"The Book of Disquiet" is a posthumously published work by the Portuguese writer Fernando Pessoa. It is a collection of fragmented thoughts, reflections, and observations that explore themes of existentialism, identity, and the nature of reality. The book is presented as the diary of an alter ego named Bernardo Soares, who expresses feelings of disquiet and alienation in a modern world. The text is notable for its poetic prose and philosophical depth, often blurring the lines between fiction and autobiography. It offers readers a glimpse into the inner life of its narrator, capturing the complexities of human emotion and the search for meaning in everyday experiences.