Very good documentary, like all those in this series. Told as a story, this book is very easy to understand, even for less than 4 years (I read it to my daughter since those 3 years), the illustrations are full of small details that my daughter loves to discover and re-discover for each scanning. Personally, I particularly appreciate the introduction of a specific and very precise vocabulary which often seems too complicated by adults while in contrast, young children easily assimilate!