The author states in his introduction that this book was consciously written in a vocabulary comfortable for the average 10-year-old. This is not, however, the usual fare offered this age group. It is really blunt about the basics. Mr. Johnson, the Director of Development at Germantown Friends School, has a firm way with figures; for instance, he gives the average size of an erection, the usual positions in human sex, the likely number of times a married couple will have intercourse. Further, he describes the various methods of contraception, the incidence of homosexual response at the adolescent level and the nature of masturbation. The book is clear, direct and written with dignity. It deals with exactly the specific questions that do arise to plague the juvenile imagination when it has been surprised by the facts of sex. There is a whole school of thought that lingers over the beauty of the birds and flowers concept in sex instruction. This book will undoubtedly make proponents of this view eat grass. There is certainly a place for this kind of plain language and, in the words of the publishers, ""The degree of selectivity to be used in recommending the book... in your particular community must be decided on the basis of your own examination of the book.