As for the actual content of _The Archetypes of the
Collective Unconscious_, I would describe it as an overview and recapitulation
of many of Jung's key concepts. As the title implies, the main concepts are archetypal images (as revealed in to people in dreams) and the
collective unconscious. These are trademark Jungian concepts, and Jung devoted a large portion of his writings to explaining what he meant by Archetypes and the collective unconscious. If I could explain it to you right here I would, but Jung spends a the first two hundred pages of this book simply explaining and defining archetype and collective unconscious. These are key concepts in understanding the human mind, and may help unlock the mysteries of conscious existence; it is by no means superfluous to devote such rigorous study to these ideas.
There is also a pictorial section of the book in which Jung actually shows examples, in the form of paintings, of archetypal images that were seen by his patients in their dreams and subsequently drawn by the patients themselves. Some of these paintings are very artistic, and there are uncanny similarities among many of them. This pictorial section occurs about 200 pages in. After the pictures, Jung goes into a detailed explanation of each one, which I found to be somewhat tiresome, especially considering many of the paintings were extremely similar. Overall, the final, brief, section of the book in which the paintings are described is quite boring, and I would recommend that the reader simply look at the paintings and forego the final explanations, which are extremely redundant. In other words, read the first two hundred pages, look at the pictures, stop, and then move on to _Aion_. The weakness of this final section is not enough to justify removing a star from my ratings, however, simply because of the utter profundity and potency of the first 200 pages, which represents the majority of the book anyway. Keep in mind that the vast majority of Jung's writings consist of essays not more that 100 pages long each. You will find that most of his complete works contain numerous profound and insightful essays, occasionally laced with the odd, specialized, highly esoteric essays.