This was the first meditation book I bought back in the early 1980s when there was little out there to choose from, waaay before the mindfulness revolution.
Although it focuses on the specific technique of zazen in the Japanese Zen tradition, it's still one of the best books I have on the exact specifics of the meditation art. Each chapter provides a physiological-scientific approach, detailing the physiology of sitting posture, breath and breathing, spine, stomach, lungs, spleen positioning, breathing rhythms and air flows, an entire chapter on the physiology of attention and its connection with breathing and posture. Later chapters describe the various mental-body states that arise as a practitioner achieves deeper levels of relaxation and shamatha (calm-abiding), what the author calls "off-sensation", followed by an intermediary state of calm, prior to kensho which, in Zen, is considered a plateau achievement. Can't remember how kensho is related to satori but these later chapters give detailed descriptions of what a practitioner can expect as her practice advances.
This is an outstanding volume on the science of meditation from a Japanese Zen perspective, discussing both the physiology of meditation as well as the subjective-phemonenological milestones and benefits of the practice. It's still one of the best books on meditation out there.