The really quick, really accessible version is the Extra Credits videos, though understand that they simplified a lot of things, and made some mistakes (which they admit to in a follow-up video).

The Great War YouTube channel also covers some of the same ground in an accessible but more rigorous manner, though I don't remember them going over all the "clash of empires" background stuff.

On the far other end, I liked the book The War That Ended Peace by Margaret MacMillan. It's a dense tome, but it's chock full of details.