After 20 years of meditation practice with teachers in Burma, not satisfied, Bhante went to a cave and spent three months, with a cobra for company, and studied the original texts and practiced. Amazing and very different results arose for him. He was stunned to go deeper faster than he had ever experienced. Awakening was real.
All aspects of breath and metta meditation are covered as what suttas are used as references.
A lot of time is spent going through the Anapanasati Sutta to show that the Buddha defined Mindfulness as how mind's attention moved - not focusing on sensations or even the breath. It is a purely observation of mind's activity, relaxing and tension and tightness that arose that drew you out of the present moment.