I ordered these books for my colleague and they are sitting beside my yet-to-review-artbooks box.
They are distracting me from my art books because they are a real joy to read. Funny and educational. They are for kids, probably around 7-12.
The books are available individually as well as in a box set. The box set is more economical, not to mention if you're ordering from overseas you just have to pay one per-item shipping charge.