Your mileage may vary. The first time I read the Silmarillion it was like reading a phone book of Middle Earth because it's seemingly just a bunch of names assorted to unclear actions and every character has multiple names in various languages or depending on which era it is happening.. but after all these years and reading through it multiple times, there are some genuinely awesome parts to it too. The Fall of Numenor, the creation of Arda by Illuvatar, the Darkening of Valinor, everything involving Morgoth, Ungoliant, etc... that would make for some pretty epic visuals, but I can't see an actual proper story being written for a movie for this kind of book. It's my definition of unfilmable, at least in the current movie format and how you need to make a movie for it to be a success.