Holmes was a prolific writer, and a late-arriving student of Emma Curtis Hopkins, the woman most people consider the grandmother of New Thought, the teacher of teachers.
Holmes was obviously a charismatic and energetic man, because he established a religious empire which is still going on today. One of its most illustrious followers is Louise L. Hay, probably the most famous exponent of New Age beliefs in the world.
The basic philosophy of Science of Mind is pretty much the same as you would find in Unity or any of the other New Thought based churches. Also known as Religious Science, its founder Ernest Holmes never really intended it to be a new church. The magazine Science of Mind, which has been in continuous production since 1927, certainly has a readership well beyond the church membership, and many subscribe to Holmes' ideas without declaring themselves a formal part of the movement.
The fundamental idea behind Science of Mind seems to be that we are created perfectly, just as God is perfect, and so we are capable of achieving anything. We are all moving into a new age of possibility, and if we can align our thoughts with the energy of the Divine, we can become a race of supermen.
Like much New Thought philosophy, Science of Mind flirts with the fringes of spiritualism and Theosophy, and Holmes' magnum opus is littered with tantalizing references to the extraordinary possibilities of the human mind freed from the old ideas of negativity. The book itself is reasonably difficult to read these days. Its enormous size and frequently prolix style means that it is best consumed in small bites, rather than sitting down to read it from cover to cover.