Like Selma Fraiberg, psychologist Kaplan writes of childhood in almost lyrical terms, charting the preliminaries to the ""second birth,"" a concept that comes from Margaret Mahler's work on separation and individuation. Her book is, according to Mahler's endorsing introduction, a translation of those ideas ""into generally readable English."" Kaplan dramatically represents the child's topsy-turvy perceptions in this growth process as she synthesizes Mahler's discoveries and the related insights of other theorists (Winnicott, Spitz, Piaget) with her own clinical experience. She describes the physical and psychological changes that make the child's acceptance of this separateness possible--recognitions of mother, of others, of beyond-the-lap and upright advantages--until the milestone arrives with all its stretching implications. ""It is well nigh impossible for a mother to satisfy a toddler in the throes of the complex dilemmas of his second birth,"" yet its successful completion matters in future development. Parts of this book are too effusive: the young child's ""elation is the vermilion overstatement that blots out the nuances and tints of ordinary life."" But much of it is direct (""The child who is having a tantrum counts on his parents not to disintegrate with him"") and some approaches poetry. Of early discoveries of sexual difference (although some feminists disagree): ""The little girl sums up her observations with mistaken algebra."" Directed to ""the educated public"" and selected for serialization in Redbook, this is too demanding to be read, like Spock or the Princeton guides, on the fly, but it may appeal to those looking for more than simple descriptive information.