I'd say it's more a graphic novel/novelty book than a nonfiction title. The little jokes, poems and so on made me confused as to which parts were true. It's blurbed by Lemony Snicket and the subtitle says "a mostly accurate account of some of earth's strangest animals." I didn't agree that all the animals were unusual, but as the author says it's really just the creatures he thought were weird.
Some things like the Axolotl are pretty weird. Others, like the Bar-Headed Goose are impressive, but not what I'd call unusual. I wouldn't have called the wombat unusual, but that was before I encountered THE WOMBAT SKEPTICS, so now I'd say it warrants inclusion. I'd heard of most of the creatures, but I read a lot of animal nonfiction so that's not surprising. Series type nonfiction books I mean. The last time I showed kindergarteners a picture of a narwhal they said it was a unicorn, so...yeah.
There's also information on classification, contrasting lists of ordinary and strange creatures, an index, a section on conservation, and two pages listing the kickstarter supporters, author's websites, CD of songs about unusual creatures, etc. There are no sources for the information included in the book, although presumably there are some on one of the author's websites perhaps.
I thought the sudden break into conservation tips was weird and I personally prefer photographs in nature/animal books, but as I said earlier I wouldn't consider this a strictly nonfiction book, not the kind of thing you'd read for a report or to learn more about a specific creature.
Verdict: This will be popular with kids who like weird and wacky facts and want a nice, oversized book to dip into and exclaim over and giggle and tell their friends that wombats have square poop. Just for this, it's worth adding.