Writing a picture book in a sketchbook... what could be more natural?

Creating a book - I'm busy painting characters for my next book, and they're coming along very nicely. They've finally made the jump from my imagination, onto the page - yes an actual paper page...! It's a picture book and I'm drawing and writing it in a sketchbook, it seems the characters are happier to jump into a sketchbook than onto a computer screen, and who can blame them...