Game of Thrones
OK, I've only seen a trailer and a snippet, but I did read the first four books. The ratio of good to lousy fantasy epics is approximately 3/a zillion. GOT is not one of the former. Like many another talented writer, George R R Martin tried to stretch a knack for suspense, scene, and creepy effects into an epic. Bad idea. Like many others, he ran out of gas and started multiplying plot themes like rabbits, and the whole enterprise ground to a halt like an armored vehicle in deep mud.
Edgar Rice Burroughs, the grandmaster, never succumbed to the epic temptation. Instead he wrote linked but self contained stories with common characters.
It's possible, of course, that a bad book (or five) can be made into a decent movie. Maybe that has happened.