How High is the Sky? by Anna Milbourne
This is another magical picture book following Pipkin the little penguin with big ideas. Pipkin the smallest penguin is always asking questions, but what he wants to know most of all is how high is the sky? So, he sets off to see how far up the sky goes and finds that it really is very high indeed. There is a special fold-out poster at the end of the book that shows Pipkin climbing into the sky, showing how high up things really are. This book is gorgeously illustrated by Serena Riglietti.