The continuing analysis of the writing process.
It's not so wide-open as it was in The Return of the Shadow, since the prior story imposed definitely constraints. But he's still sorting out which hobbits have what names, and which ones will go. At one point Elrond firmly puts his foot down on the notion that either Merry or Pippin can go. Sam didn't always go with Frodo after the split up, and sometimes he was the first one to see Gandalf again. Eowyn was considered as a love interest for Aragorn, but only briefly. And her cousin, Theoden's daughter, didn't exist for long. At one point Boromir and Aragorn made it to Minas Tirth together, and Aragorn got chosen as Lord there, to Boromir's jealousy.
Interesting to watch the provisional status of everything fixed in the final version.