Yes, later. As a great Tolkien scholar once wrote, "If we pick these things out of the scrap heap it is only to show how wise the author was to throw them there." But in fact there's much more to the posthumous books than the LOTR scrap heap. Some of his best work is also in there, including things relating to The Silmarillion that are far superior to the book of that title. (One of my tasks is to explain why they're better.)

But, again: later. LOTR first.