Keeping the Breath in Mind & Lessons in Samadhi is written by Ajahn Lee Dhammadharo. It teaches mind freedom as a very fundamental technique that begins with maintaining the breath in mind, rather than as a mind-boggling philosophy. The teachings here are based on the works of Ajaan Lee Dhammadharo a well-known Buddhist meditation instructor in Thailand.
Ajaan Lee was a forest monk which means he chooses to live in the seclusion of the forest and makes meditation the core topic of his practice. As a result, his teachings are based on personal, practical experience, while he also makes a point of tying them to Buddhist philosophy.