Books about the body!
These next two photos are from Look Inside Your Body. The youtube flip through of both of the Look Inside and Lift the Flap Body books can be found here.
How your Body Works example:
The Shine-A- Light book on the body is pretty amazing as well. This is in picture book format and each page talks about different parts of the body. Not as detailed as the Lift-The Flap or Look Inside counterparts, yet illuminating in their own way. One one page a girl is playing soccer. When you hold the picture up to the light, you can see how her muscles extend when she kicks.
The Youtube link for more detail on this book and others in the Shine A Light series can be found here.