Episodic and ultimately forgettable little children's confection. Because I live under a rock, I was not aware this was as old as it is - originally published in 1964! - so I found the early 60s-era drawing style and weird historical tics in the writing affected. For example, the parents are referred to as Mr. and Mrs. Lambchop throughout the book, which struck me as odd and distant. What's wrong with Mom and Dad? But then, whoops! It's not affected, it's just the way things were written then.
But. Dad showed up at my door a while ago with a Flat Stanley and a camera, so he could take pictures with his grandkids and Stanley to send off to someone else with grandkids, a sort of existential Marco Polo, though images, pictures of Stanley and children winging around the globe. (There's an episode where Stanley's parents mail him to friends in California, which is where this idea started, I think.) This is, as the kids say, adorable.
I like when books create or perpetrate these real-world engagements, even if the book doesn't explicitly create them. So, two stars for the book - it's mostly only ok, except for a sequence when Stanley and his brother have an affecting conversation about sibling rivalry - but an extra star for the fun that's had in it's name. I wish I felt comfortable posting pictures of my kiddies with Stanley, but I don't, but rest assured they're the best ever.