Book of Gramarye

Literally, a book of magical "grammar"--knowledge, spells, and wisdom. A grimoire. Both "gramarye" or "gramarie" (Middle English) and "grimoire" are probably from Old French gramaire, "grammar". The word glamour is apparently a corruption of grammar, (if I'm to trust the dictionary), and thus the relation of the ideas of "glamour" in the magical sense and grammar in the magical sense--particularly the idea that those who can read and write and have their own books.

The Book of Gramarye is also the name of the great book of the Old Ones in Susan Cooper's The Dark Is Rising. On Christmas Eve, Will Staton is taken through time by Merriman Lyon to a Christmas party held at the manor house near Will's home. Here, he is able to read the Book without the attention of the dark. Once he has read and memorized it, the book is destroyed, so that none of The Dark can ever read it.¹

The snipets of text that we get from the Book seem to show it as a collection of what we know as medieval Welsh literature--there are portions of Taliesin's poems, the Triads, bits of the Mabinogion, strewn together. If anything, Cooper's Book of Gramarye seems similar to the real-world Myvyrian Archaiology, an 19th century collection of medieval Welsh literature and history. However, it is also combined with what are obviously "spell book" staples--section headings include things like "on flying" and whatnot.