In its ability to combine profound spiritual teachings with far-reaching psychological insights, acim is unlike anything that has gone before. As the New York Times described it in 2019, the Course could be called “the esoteric bible that went mainstream,” and it has certainly been a major influence on the rapidly growing group of people who identify as "spiritual but not religious."

First published in 1976, A Course in Miracles—often simply referred to as ACIM—combines Christian language and metaphysics with more contemporary Western psychology and Eastern mysticism. Bill Thetford once called it “the Christian Vedanta.” It directly challenges many of the doctrines of Christianity, including its belief that Jesus died on the cross to atone for the sins of humanity and that there is only one reality—that of God’s love.

A Course in Miracles focuses on forgiveness as the key to transformation and encourages its students to apply forgiveness to every area of their lives. While many spiritual paths and therapeutic methods also teach the value of forgiveness, ACIM is unique in its relentless emphasis on the practice of forgiveness as a moment-by-moment discipline to change attitudes and behaviors.

Although the Course is not widely taught in churches, it has attracted a number of prominent teachers who have made it part of their own practice. These include Marianne Williamson, Wayne Dyer and Gabrielle Bernstein. The major New Age publisher Hay House bought the rights to the book in 2005, and the author Gary Renard has written three subsequent books influenced by the Course.

The Course is available in Acim numerous editions, and it has been translated into 27 languages. However, the most popular and reliable edition is the Standard edition published by the Foundation for Inner Peace. It has maintained annual sales of about 3 million copies and is a perennial best seller.

The annotation system of the Standard edition enables readers to reference passages within the text and its Supplements, even between different translations. This system consists of superscript numbers that refer to the paragraphs and sentences within each paragraph of the text, and it helps students to locate specific sections of the text quickly and easily no matter what version of the text they are reading.