The Unexpected Dimension is a 1960 paperback anthology of science fiction short stories by Algis Budrys. It only merits 3 out of 5 stars on Goodreads, and even this 5-star review on Amazon gives me pause: "Budrys is a difficult writer. It usually takes several readings before you can really understand what is going on in his stories." I'll pass, but I give the cover illustration by John Blanchard 5 stars! Check out a few of his other covers here: