[Zigûr]

I used Arda Reconstructed in my PhD research so I've read some of it. It's useful as a reference for distinguishing which bits are genuine J.R.R. Tolkien, which aren't, and where they came from, but it doesn't propose a "true" Silmarillion if I recall correctly. It's an interesting read and worthwhile if you want to be redirected back to works found in earlier History volumes which form the Professor's own final say on various matters he never got around to revising.