The value of a book is a shifting quality, as a number of dimensions are involved in the cumulative judgment thrust upon it. One dimension is time: say, a given Practice of Physick may have justifiably held a pre-eminent place in the 18th Century, for what it taught was then held to be truth. Another dimension is place: the superb Perspectives in Malnutrition (Joseph Gillman and Theodore Gillman, 1951) for example, has preeminent utility in Africa, for the nutritional problems and anomalies so marvelously described therein were tested in the African milieu; they apply more specifically to nutritional problems in Africa (though for the United States the book has a heuristic value).
But at all times, the third dimension is the reader. No book is good per se unless the nature of interest and the level of the reader for whom it is good, are mentioned. (Parenthetically, the converse is