Before You Were a Baby,

This is a great book for a detailed introduction to reproduction. It contains all the proper terms for male and female anatomy along with simple non-offensive illustrations. The anatomy is diagramed, and the hows of intercourse are explained in words, but there are no diagrams of intercourse. It goes into specific detail about human reproduction and sexual intercourse in a very easy-to-understand format for elementary-aged children. This book explains the anatomy and the hows of reproduction from intercourse up to birth with just the facts, without comments about love, marriage, or religion, so anyone who wishes to explain the specific details to a child could do so with this book and then add one's own beliefs to supplement it. It is out of print, but not out of date.