My son really likes this book, and I think it's a lovely introduction to Hundertwasser's art and philosophy. He is a somewhat "eccentric" artist and the text and overall composition of the book reflects that. Contrary to the other reviewer, neither my son nor myself thought that the book was badly translated; it is a little "odd" in places but I just felt that reflected its subject matter rather than the quality of the translation!
The book contains many suggestions for imaginative activities; not just "artistic" ones, but also things that stretch their imagination and understanding in a more general way.
I think this book is a wonderful introduction to art for children; it is much more engaging than many books about art aimed at kids. This is partly because of the way the book itself is written, but must be due in a large part to the vibrant and exciting style of Hundertwasser's art, which this book presents very well. I think there is something about his creations that particularly appeals to children, more so than many artists at any rate!
I think that this book could suit quite a wide range of ages; very young kids would probably enjoy looking at the pictures, and older kids wouldn't feel that it was "talking down to them". I gave my son this book when he was seven, he is now nearly nine. Teenagers might be a bit too old for it, but it would probably still appeal to younger teenagers with a good imagination and an enthusiasm for creativity.