The Ascended Master Gautama Buddha was embodied as the historical Buddha 2,500 year ago. As Christianity has elevated Jesus to being different from other people, some Buddhist teachings have done the same with Gautama. However, Gautama was created as the rest of us and had many embodiments before reaching the level of consciousness that qualified him to carry out the mission of demonstrating the path to Buddhahood.
Gautama hold the office of the Planetary Buddha and also holds space for the earth. This means that Gautama is holding the spiritual balance that allows space to exist in a form that is behind the evolution of the rest of the universe (meaning matter is more dense). This is what allows free will to outplay itself as it currently does on earth.
Invocations to Gautama Buddha
There are invocations to Gautama Buddha in several of the books about changing world conditions.
Books by Gautama Buddha
There is no book specifically by Gautama Buddha, but there are dictations from him in several of the books about changing world conditions.