Some books are timeless. Mumkin is not. Since this was first published in 1986, the story now seems saccarine and naive.
I bought a paperback in the early 1990s, since I'm a sucker for Robin James' art. Stephen Cosgrove dedicated this book to "two great men in Geneva who could imagine a world without borders of thicket and vine." When I first read that, I knew exactly who he was talking about.
After reading this again at the age of 54, I have no idea who he was talking about. They couldn't have been that great, since borders are highter and tighter than ever. That dedication was such an Eighties thing to do, Cosgrove. I was guilty of thinking like that, too, in the Eighties.
Quite frankly, I think Mumkin had the right idea. He just forgot about a water source. If he'd put his border up around part of the stream, that border would still be up today. It's not that sharing sucks. I have no problem with that. It's just that everyone else has to shit all over you. Now, ponies and horses need each other. They have safety in herds.
People, though ... not so much. Paradise would be if humans never existed.
So ... I'm not a fan of the text, but the artwork is incredible. Mumkin is a dapple grey. You know how hard that is to paint? And yet James manages it. You can practically touch those dapples just by looking at them. She also gives the pony herd a rainbow of equine colors, including blanket spotted, pinto, another kind of grey, Palomino, and a killer liver chestnut.
You can go The Open Library to laugh at the text and soak in the illustrations. Do it soon, because you never know when a book's going to get removed.