There are no sources or bibliography; the only backmatter is a page of additional facts.
I had to read the book more than once to really get used to the sometimes flimsy segues. It starts with some facts about hippos, including that they can't swim...but sea turtles can swim and go faster than you think, much faster than jellyfish...speaking of jellyfish, here are some facts including that some species have bioluminescence...like fireflies! who can be different colors...unlike zebras who aren't lots of colors but have interesting patterns and are attracted to black and white things...not like racoons who like shiny things and can be found in garbage cans....on the other hand, chipmunks are more likely to be found in the woods, filling their mouth pouches with food for hibernation...kangaroos have a different use for their pouches, here are some interesting facts about their jumping abilities...another animal that jumps is a rabbit, did you know rabbits live underground? Bats, on the other hand, may live above ground or in caves and sleep all day...not like ants, who live underground but are awake a lot and live in colonies....like herons who are really tall....but hummingbirds are small....blue whales are bigger than everything "And unlike hippos...blue whales sure can SWIM!"
So, that's a LOT of facts packed into this little book. The illustrations are cheerful and definitely attractive with bold colors and lines, pop-eyed cartoon animals, and funny details like speedy sea turtles in sweatbands and chipmunks with food pouches distended bigger than their entire bodies.
Verdict: This wouldn't work well for a school report or an older kid wanting to learn about a specific animal and it's too long for storytime or reading as a story to a little one, but it's just right for that in between age of 1st - 3rd grade when kids really crave collections of facts and will enjoy the cartoon animals. You can buy this whole series in paperback, but I would expend the extra money to get them in hardcover as they will see a lot of use.