Summer (the book) is unique. And like Summer (the season) it is not a story for everyone. There is a more sophisticated feel to the story tht makes it sometimes a bit dusty. Yet, there is also this story about friendship, sharing and learning about the grasslands that gives an adventure to the reader.
The illustrations, however, by Yu Rong, are strong and different. Their colors are the perfect amount of sharp and muted; bold and subtle. They capture the grasslands perfectly with color and the fact that 
there is just the right amount of details on the pages that need them. Some pages, however, have little detail to allow you to focus on the story.
Cao Wenxuan put much story and feeling into the text. There is lots going on that will resonate or not differently. Even the size of the pages changes to show you action of the story. This clever way of presenting story and art makes this a unique book.
The interesting element to the story over all is both authors are Asian and some of this background makes its way into the story. This also might explain why a brown bear and a jackal are in the same grassland. My limited understanding of grasslands made me think this animal paring was not something one would see.
While longer and a more poetic text, this book is not for the very young, yet the theme of friendship, selflessness and helpfulness is for all ages. Perhaps good for a classroom read aloud, but a one-one-one feels more appropriate.