My wild guesses were and not backed up here by facts either ( it's just an assumption only ) . That the props department had either took some old books saved from other older movies from many years ago and used them . Also the books could have been deliberately water damaged in some sort of " aging-like process " perhaps using some books old or new and then let them dry completely so the paper material would become very weak and fall apart easily . After all the book in George's hands the pages looked a bit water damaged before he crumbed it up . I thought it was an excellent effect ( and a bit sad too ) to have seen books so far degraded like that before . Thanks nycruise-1 for your subject post .
I suspect there was only one book. The rest on the shelf was a construct to look like a row of books, but really was something that could be destroyed with the swipe of his hand.
... and the rocks it pummels. - James Berardinelli
The effect of sweeping all the books into dust was probably achieved by sculpting the row of books out of damp sand or some powder (I mean as a single lump of sand made to look like a row of books) and then painting the side to look like the spines of the books.