What I loved: The realistic illustrations and diversity of animals shown are really great, and children will love looking at the near-photographic images of animals. The phrases are simple and easy to understand, making them great for young readers. They are all written on a colored bar below the illustrations that makes the writing clear and easy to read. Another cool feature is the small print that gives the animal's species below its image, so that parents can identify exactly which animal is shown, even for ones that are less well known.
What left me wanting more: On the page that says "Some mammals eat animals," there is an image of a bobcat holding a deceased rabbit. This may be troubling for sensitive children, and while it is a fact of the wild, it may not be one all children are ready to discuss. The following page which shows a squirrel eating a moth (for "Some mammals hunt at night") is less troubling than the bunny. This will certainly depend on the reader, but is worth noting.
Final verdict: Overall, this book is a simple introduction to mammals with basic facts and realistic illustrations.