Had James George Frazer changed career and become a psychologist, after writing his masterpiece, this is something I imagine he could have written as a sequel. Like the Golden Bough, Archetypes and the Collective Unconscious has a distinctly scientific feel, something often found lacking in the soft (social) sciences and humanities, this sets the work out as something to be taken serious notice of.
Jung sets out to explain the workings of the human mind, why it shows certain patterns, and why these patterns recur; comparable and parallel to Frazer's exposition on how religion and magic evolved across time and the world, what patterns occur, and why. Jung believes, and seeks to show, that the unconscious human mind has evolved to contain deeply embedded psychological structures called archetypes, which if understood could not only explain normal and abnormal human psychological behaviour, but the behaviour of mankind across the ages, why we have created myths, rituals and gods, and why they consistently share certain features.
This is one of those books that has to be read to be appreciated, and perhaps has to be read with a knowledge of certain other works to be appreciated to its full extent. From a biological viewpoint the archetypes are not particularly supported in the book, but it is clear to see that they would have evolved in the ancestors of man while the brain on the whole was lacking a capacity for advanced consciousness in order to provide creatures with relatively complicated instincts that would increase their survival value; one illustration I can think of would be the fear of snakes, observable in humans and primates which have never encountered a snake before. This recurrently turns up not only in mythology as the dragon, in religion sometimes representing the devil, but also in many of the contemporary psychological studies present in this book.
Also, taking up quite a lot of this book, are the case studies of patients who Jung has either dealt with or has notes on, in which he finds evidence for his archetypes, using the archetypes to satisfactorily diagnose what is wrong with them.
This book I would recommend to anyone with an interest in the human condition. ( )

One of the high-water marks of Jung's work, in which he defines archetypes, describes the anima, animus, child, and mother archetypes. Jung also lays the foundation for the structure of his theory of a collective unconscious, which unites us all at a deep level of our unconscious and explains how contemplation of myth and fairytales provide portals to this level of mind, which is laden with treasure and intuitive knowledge. Of the Jungian works I have read, Archetypes and the Collective Unconscious and Symbols of Transformation were works of outstanding merit. The author was one of the seminal thinkers of the 20th century, and subsequent explorers such as James Hillman, Ken Wilber, and others continue his work into the future. In Archetypes, Jung also discusses individuation, in which the unconscious is brought into the light and united with the conscious mind in order to integrate the individual and bring about wholeness, and the function of mandala symbolism is explained. It is recommended that one should probably read an introductory book to Jung's thought, before tackling his major works. ( )

Jung opened up the unseen world for me. Before Joe Campbell came along, Jung taught that ghosts, demons, planets in trine, the Knave of Swords, alchemy, religions, and myth all pointed back to the interior of the human spirit. ( )

If you don't mind slogging through heavy academic works, this book has a lot to offer in terms of explaining Jung's concept of the collective unconscious and how archetypes operate in individuals across cultures. ( )