The Secret Life of a Snowflake An Up-Close Look at the Art & Science of Snowflakes by Kenneth Libbrecht is the best book I've found yet for looking at the science of snow flakes.
Have you ever wondered how snow flakes form? Why are they all different? Why do they always have the same amount of sides or arms? Why do they look white in a group but under a microscope they look clear?
This book explained everything we wanted to know and the pictures are amazing.