Sigmund Freud 
Group Psychology and the Analysis of the Ego [EPUB ebook] 

In
Group Psychology and the Analysis of the Ego, Freud explores theories on group dynamics and how psycho-sociological forces shape personality. He argues that an individual derives security from being part of a group, what he terms ‘the Herd Instinct.’ However, this feeling of belonging leads to a loss of the individual’s consciousness. Other topics covered include Being in Love, Suggestion and Libido, and Identification.
This new 2018 edition of
Group Psychology and The Analysis of The Ego is a revised translation of the James Strachey version in modern American English.