In the two-part series they reference three books that have something to do with the Holy Grail.
I didn't quite pick up on what the books were about save for their titles:
The Book of Numbers
The Book of Potions
and The Book of Words.
Below I've attached screen-caps from the movie of the first two books (the book of words was only shown in wrappings at the end).
It appears as though the book of potions is a coptic-style book where the pages are sewn to each other and then to a cover. The book of numbers, however, appears to a period bind from around the 1200's when the movie was set.
|Cover of Book of Numbers|
|Cover of Book of Potions|
|Internal shot, Book of Numbers|
|Cover of Book of Numbers with what appears to be leather straps for tapes.|
|Spine of Book of Potions - notice the tied cords.|
|Cover of Book of Potions, notice what appears to be a metal plate on the cover as decoration as well as the hidden cords on the spine.|
|More detail on the cover of the Book of Potions.|
|Scan from one of the pages of the Book of Potions.|