Personally, I would price something like that at (granted ranks) cubed times 1,000 gp, with a book granting 5 ranks being the absolute limit. So such a book would cost as follows - 1 rank, 1,000 gp - 2 ranks, 8,000 gp - 3 ranks 27,000 gp - 4 ranks, 64,000 gp - 5 ranks 125,000 gp.
Also, ranks...