Viktor Frankl's 1946 book Man's Search for Meaning chronicles his experiences as a concentration camp inmate and describes his psychotherapeutic method of finding a reason to live. According to Frankl, the book intends to answer the question "How was everyday life in a concentration camp reflected in the mind of the average prisoner?" Part One constitutes Frankl's analysis of his experiences in the concentration camps, while Part Two introduces his ideas of meaning and his theory of logotherapy.

According to a survey conducted by the Book-of-the-Month Club and the Library of Congress, Man's Search For Meaning belongs to a list of "the ten most influential books in [the United States]." (New York Times, November 20, 1991). At the time of the author's death in 1997, the book had sold 10 million copies in twenty-four languages.

Frankl identifies three psychological reactions experienced by all inmates to one degree or another: (1) shock during the initial admission phase to the camp, (2) apathy after becoming accustomed to camp existence, in which the inmate values only that which helps himself or others survive, and (3) reactions of depersonalization, moral deformity, bitterness, and disillusionment after being liberated.

Frankl concludes that the meaning of life is found in every moment of living; life never ceases to have meaning, even in suffering and death. In a group therapy session during a mass fast inflicted on the camp's inmates trying to protect an anonymous fellow inmate from fatal retribution by authorities, Frankl offered the thought that for everyone in a dire condition there is someone looking down, a friend, family member, or even God, who would expect not to be disappointed. Frankl concludes from his experience that a prisoner's psychological reactions are not solely the result of the conditions of his life, but also from the freedom of choice he always has even in severe suffering. The inner hold a prisoner has on his spiritual self relies on having a faith in the future, and that once a prisoner loses that faith, he is doomed.

He also concludes that there are only two races of men, decent men and indecent. No society is free of either of them, and thus there were "decent" Nazi guards and "indecent" prisoners, most notably the capo who would torture and abuse their fellow prisoners for personal gain.