The Mysteries by Bill Watterson and John Kascht (Watterson wrote and illustrated with Kascht also illustrating) is very odd and very amazing. It is an experience book. The authors/illustrators are geniuses and seriously disturbed. The black and white illustrations make for a unique read.
If you like Calvin and Hobbes (Bill Watterson’s signature creation) and its darker side (and it can get deep) then I would say that you are still not prepared for what is happening. I am not familiar with John Kascht and their work, but I am assuming they might be a bit on the edgier side. The story itself is simple: People fear The Mysteries. They make up stories about them. Each one is worse than the other. Their art is also representative of what they think The Mysteries are. That is until the King finally, tired of the fear and the unknown, sends his Knights out to search. None return until one, tired, haggard Knight brings a Mystery back. 
And this Mystery is… nothing. Not the monster and demon they feared. Therefore, they decide to take down the walls that protected them, will learn more things (airplanes), expand and they even laugh at the fact that anyone feared them. Of course, we the reader knows (due to the image this text is placed with) that we should be afraid.
The theme of course is deeper. It is the fear of the unknown and then the learning of it. But then the ignorance of ignoring the dangers. And the fact the Mysteries are just waiting for their time to shine. This is shown by the fact things are black and white, hazy and sometimes feel grotesque, but are hauntingly beautiful. The artwork is more the moving force of things, and not the text, as I have probably written more in a few lines than the entire book has. The set up is a picture book, but is not for kids. It is a mature allegory.
