Books of Glyph Mastery are currently needed by scribes in order to learn all the glyphs in the game. While they will eventually no longer be needed, they will always be useful. Even when Blizzard gets around to letting you research all the glyphs without them, those research recipes are both on a one-day cooldown, and the books can be used to continue learning. These books are an excellent candidate for "flipping" for a few reasons. Let's look into why and how to flip them.
Bad for the market?
Speculative flipping is not bad for the market. First, when people say "bad for the market," they mean "bad for people who need to buy glyph books." While flippers seem to be making money from nothing, they're actually making money from risk. They buy up excess stock in times of plenty and sell it in times of scarcity, and this protects book buyers from having to deal with a nearly empty auction house as often. All flippers do is make it so that when a couple of new scribes start buying books by the wheelbarrow and completely empty the AH, they won't have to wait for more stock to trickle in from people leveling through Northrend.