I just picked up a copy of Euclid a couple weeks ago, myself—I've only ever gone through abbreviated versions of it, and never the whole thing. (It'll be a while before I do go through the whole thing, but...) I spent a little while flipping through it and what surprised me most is that so little of it is what we, today, call geometry! Most of it is concerned with arithmetic and number theory, and only a few of the books are about geometric constructions proper!