As I mentioned, the Tolkien material in The Fall of Númenor has been published already. If you have The Silmarillion and Unfinished Tales, you've got by far the most of the text here. That is, you'll have the Akallabêth and the tale of Aldarion and Erendis ("The Mariner's Wife"), the Description of Númenor, & the list of kings ("Line of Elros"). You'll no doubt have LotR, which contributes to The Fall here and there.
Tolkien's Letters, with his 1951 long outline of his work written for Milton Waldman, supplies perhaps a few paragraphs.
The Fall is physically well made, with pages in sewn signatures. But if you read the items listed above, especially the Akallabêth and "Aldarion and Erendis" (Silmarillion, Unfinished Tales), you'll have the most interesting material under your hat. The Aldarion and Erendis story (Unfinished Tales) is a study of an unhappy marriage, a story unusually grief-stricken for Tolkien.
"...they lavished wealth and an on tombs and memorials" (sic, p. 172).