2150 AD is a novel copyrighted by Don Plym and Thea (Alexander) Plym and originally published in 1971. In 1976 it was modified and re-published by Thea Alexander. The story concerns the character of Jon, who travels between his world of 1976 and the future world of 2150, where the Macro Society dominates the Earth. The world of 1976 is referred to by the inhabitants of 2150 as the pinnacle of micro society.

This book is based on the journal of Jon Lake, who lived in the 1960s and '70s as a psychiatrist. Because of his life experiences and accepting world view, his soul was considered evolved, or Macro, enough to travel to 2150 where his twin soul, Lea Nine, and soul mate, Carol Three lived. His astral form traveled to 2150 and he lived there while his 1970s body slept, and returned to the '70s during his waking hours.

The book is centered around Macro Philosophy and concepts such as reincarnation, karma, twin souls and soul mates, as well as macro and micro limitations. Thea Alexander started a workshop for studying Macro Philosophy shortly before the book was published; this information is on the back cover of the book.