A considered, constructive addition to the demystifying literature on the medical profession. For Preston, 20 years a physician, there are two major problems: doctors' inability to sustain the ideal of devotion to their patients' interests; and widespread abuse--or neglect--of the scientific method. ""Unscientific pronouncements, inaccurate conclusions, and delusions of infallibility,"" he writes, ""are translated into medical practices that affect the lives and health of credulous patients."" Consequently, Preston traces the roots of current medical practice, dissects the relationship between healers and their patients, and describes some of the major oddities of the prevailing system. He is especially interesting on deception in medicine. Such deception can take the form either of deliberate lying (about test results, for example) or of perpetuating the idea that a physician's own clinical judgment is superior to knowledge derived from controlled studies. We have supported these deceptions by allowing physicians to police themselves--""with no real attempt by those who receive the service to make a comprehensive assessment of it."" These are not altogether new charges; but Preston has solutions too--practical, workable ones, for both practitioners and patients. Not a tome or a tract, this should go over well with the ordinary, unagitated reader.