THE SELLAMILLION is NOT a parody of Tolkien's THE SILMARILLION. That would be pointless because although all Tolkien fans have a copy, only three of them have read past page 40.
It is, however, a parody of all that Tolkien created as he worked on LORD OF THE RINGS. The history of the elderly days. Early missing drafts of LORD OF THE RINGS. A correspondence between the author and publisher on whether it should be a Bellybutton Stud of Doom rather than a Ring of Power. An experimental version of LOTR as if written by Dr Seuss.
That sort of thing. It'll be funny. Possibly hilarious. The author's told us it will be. Promised even. And he did write THE SODDIT. And that was quite funny.