There are quite a few permutations of the Lord of the Rings films out there on Blu-ray, but the extended editions are the ones you want, and the extended trilogy pack is down to $40 at Amazon today.
All three extended films add up to 11 hours, not even counting the 26 hours of included special features, so block out a few vacation days. No wonder it’s the best selling Blu-ray in Kinja Deals history by a wide margin.