Everybody Poops 410 Pounds a Year, written by Deuce Flanagan and illustrated by David R Dudley.
This book provides a shitload of information about shit. Almost everything you ever wanted to know about the subject (it did leave a few questions unanswered).
Some things to think about "Before the automobile, NYC was so overrun by horses and pack animals that during the winter the streets were covered in five feet of ice-packed manure." I just can't get over how much the world must have stunk before modern plumbing!
How did people deal?
The illustrations in this book really work well with the text. They are amusing and also informative.