As a kid, I was fascinated with science. I was bored by the mundane and typical science projects like baking soda volcanos or the fluid dynamics of starch. What I really liked was the absurdly abstract ideas like how atoms form bonds and what it would be like inside a black hole. Unfortunately there were few lessons that covered that material for a 12 year old kid.1
One of my all time favorite books was Mr. Tompkins in Paper Back.2 It's an exploration of quantum physics, relativity and atomic structure like no other. Each concept is delivered as a retelling of the strange dreams of Mr. Tompkins the bank teller. Each dream is delightfully weird and provides a bridge between the macroscopic everyday world to the wonderfully weird quantum world.
I think this book is ideal for an elementary school age child but as an adult, I still love the hell out of it. It's also one of the clearly visible stepping stones in my path from child to scientist.