I love "It's So Amazing." I just finished teaching human reproduction to middle school kids and the 11 year olds really loved that book. It was just risque enough to really capture their interest but totally appropriate and written at a nice level. They also enjoyed "Hair in Funny Places." That's kind of a silly, but really informative, book about puberty. I don't like that it depicts hormones as nasty monsters, but it was easy enough to say just that to the kids and use that as a jumping-off point for talking about all the amazing things hormones do for our bodies. I also like "Where Willy Went", but I didn't use it with my students because it was really geared toward younger kids. It might be just right for a 9 year old, or even a bit younger.
