So a 4D being can look down on our "flat" 3D space and see everything at once, at least everything close to him. Let's say he can also drop down into our space, Flatland-style. I argue that even though he can see everything as if it were flat, he would have difficulty reading our paper books, even if he knew our languages.
Here's why:
Let's bring the analogy down one dimension. You're looking down on a 2D space, trying to read their "books." What do their books look like? I imagine they might be one long string of a scroll, or maybe a bunch of lines bound together by a spine, like the teeth on a comb. The written language might look something like Morse Code. The words are printed on both sides of the thin strands, and the ink, much like ours, penetrates the thin strand of paper to a depth of just a few micrometers. That's much too small to see from "above." And if the book is closed, all of these micrometer-thin words will be smashed up against each other, so it would look like a jumble of black and white static.
Even if you could put your eyeball exactly on the 2D plane, looking at a book like a flatlander would, you'd only see the 1D "side" of the page. I can't imagine that our eyes would see anything at all. And if they did, it'd be an infinitely-thin strand of light from which you'd need to discern the Morse Code words on the page.
Returning to thicker problems, I think the 4D being would have the same problems trying to read one of our 3D books. The ink on the pages is just too thin, and their 4D eyes aren't equipped to view 3D shapes on the 3D hyperplane like ours are.
But if you disagree, I'd love to hear why. This is a thought I've had for a while, but I haven't heard of anyone else proposing the problem. I'd like to know if my answer is totally off-base, or if my reasoning is sound.
Ready, set, debate!