I was recently looking for a tractor colouring book for my nephew, who loves tractors, when I came across this Charley Harper colouring book, in which his beautiful illustrations are stripped of colour and compiled into this lovely little book.
He grew up on a farm and worked in a studio in the woods, both of which have inspired his drawings. The animals make the illustrations perfect for a kids colouring book, although my older brother also said he wouldn't mind having this book, and I agree. (Or if you're into needlepoint, some of his illustrations are available as needlepoint kits)
I stumbled across this letter, in which he writes about his story and process. I related to his views on silk-screening as being a perfect process for reproducing prints and that the print can be even more satisfying than the original. I loved his description of trasitioning away from realism as he simplified his drawings by thinking flat and reducing the edges to staight lines and curves. He used drawing instruments like a compass, t-square, and french curve, and cut out paper for the larger shapes. I love reading other artists' processes.