I've done a few of these covers now (ten, I think) and worked on a full colour book with Kjartan, providing illustrations and strips throughout, Amazon says that book is out in April. I'm not the world's most natural cartoonist as my instinct is to 'draw' rather than 'cartoon'. That inconsistency runs through these images - cartoon schematics clashing with attempts at 'figurative' anatomy. It's a difficult balance to strike. There some very successful cartoonists/comic artists whose work has the feel of real people wearing cartoon masks which sometimes bothers me. Hergé of course solved this dichotomy with an even line weight throughout and of course delicately chosen and placed cartoon features.
I'll keep working on the cartooning because I have so much to learn and much of what I want to achieve with my writing involves cartooning well.