Aion is one of Jungs last major works, and as such is concerned with the jungian themes of individuation and the creation of the "self". Its probably a good idea if your already versed in Jungs theories: for the sake of not repeating what hes written in earlier volumes he assumes a familiarity with his previous work. Infact I dread to think what a layman not familiar with Jung would make of this work which delves heavily into the symbolism of early Christianity, Gnosticism & Alchemy in order to explain the psyche. Better to start with something like "Archetypes & the collective unconcious" (also available in paperback here in the UK)if your interested in Jungs later thought. Those who are familiar with Jung though will find this an invaluable source complementing his other writings on western religion.