I really don't know. One thing I do know, though, is that his books are fun, quirky and very addictive. We ordered Drawing Book of Animals and Fingerprint Drawing Book recently. The first we gave away as a gift, the second we kept and (armed with some of those itty bitty coloured stamp pads picked up from the craft store) set to work on fingerprinting our way through a rainy afternoon.
The first one Cee Cee did of the mouse with balloons was my favourite:
Then she was off on a roll:
There is a school of thought that says children should be left alone to draw or paint in their own way rather than be "taught" to make art. Part of me agrees but I think that these books are a special case and are really only intended as starting points for a child's own unique creations to emerge. Which they did (in our case) once the basic technique was mastered.
So, good on you Ed (whoever you are) we really like you....