It's Perfectly Normal: A book about changing bodies, growing up, sex, and sexual health by Robie H. Harris and Michael Emberley

Harris, R. (1994). It's perfectly normal: A book about changing bodies, growing up, sex, and sexual health. Cambridge, Mass: Candlewick Press. 

 It's Perfectly Normal is an informational book for young adults and children who are about to become young adults or are going through puberty or have questions about changing bodies, growing up, sex and sexual health. It also includes topics about pregnancy, birth, sexual orientation, birth control, sexually transmitted diseases, and sexual abuse.  It covers all these topics in an intelligent and clear way with the support of comic-like illustrations that simultaneously inform and provide humor as to "lighten up" the subject matter. The illustrations are a perfect choice for such a book and the young audience that it is intended for. Although it makes us want to blush at times, I would highly recommend this as a parent looking to inform their children or even to a health science teacher to use as an informative text (with parental permission). It's a book that young adults need to read just before or at the beginning stages of adolescence. It is probably the most important topic of this time in their lives and it's best to explain these topics in the clearest way possible. This book meets the needs of this age group by doing just that.