When Pigasso Met Mootisse

I actually haven't seen this book in person, but couldn't help but fall immediately in love as soon as I read the title. It looks like a fun and developmentally appropriate way to introduce modern art to kids.

From the website: What begins as a neighborly overture escalates into a mess. Soon, two artists become fierce rivals, calling each other names and ultimately building a fence between them. But when the two painters paint opposite sides of the fence that divides them, they unknowingly create a modern art masterpiece, and learn it is their friendship that is the true work of art. Nina Laden's wacky illustrations complement this funny story that not only introduces children to two of the world's most extraordinary modern artists, but teaches a very important lesson-how to creatively resolve a conflict-in a most unusual way.