Next on my list of readings on foundational Buddhism is Daniel Ingram’s Mastering the Core Teachings of the Buddha. Ingram calls it “hardcore dharma” of the “Interdependent Universe.”
This book is free as a PDF on the web:
I’m also reading Surya Das’ Awakening the Buddha Within, Eight Steps to Enlightenment. I really connected with Surya Das in one of his Tricycle online retreats. Surya Das is an American who became a Tibetan Lama. He practices Dzogchen, but teaches Dzogchen as a path that can be practiced in one’s everyday life. Awakening the Buddha Within is also about the Eight-fold Path, or foundational Buddhism.