History of Middle Earth. Volume IX
This compilation of Tolkien’s drafts and notes finishes up the end of the Lord of the Rings trilogy and adds some other writings to pad out the book to a reasonable length. I finished the first part very quickly, then ran out of steam on the new material.
The part I found hard going was “The Notion Club Papers” which seemed more like a bunch of inside jokes for his buddies at the weekly ‘literary critique” get-togethers they had. It finally started to pick up when one of them started having visions of the fall of Numenor – tied to some Anglo Saxon root rather than Middle Earth.
Then in the last section, he lifts the good parts out of the Notion Club and drops it entirely into his Middle Earth and we see that story get fleshed out polished.
At this point I am about half through the series – I strongly prefer the ones that follow the development of the books I am familiar with to the more detached works. If you are tempted to read these I would start with Volumes VI to IX which follow the writing of Lord of the Rings. If you don’t like those, the others are likely to be even harder to get through.