David’s in depth and beautifully organized assortment of audio teachings can be found at acim.me. The e-book is split into 3 sections: the Text, the Workbook, and the Handbook for Lecturers. All are overflowing with practical spiritual knowledge. Nonetheless the "engine home" with the Course is its every day Workbook https://awakening-mind.org/resources/a-course-in-miracles/