If you've played Weekly Snapshot 12W17A, you'll know that books now require a single bit of leather to craft. Unless you have a nicely functioning cow farm, STOCK UP ON BOOKS! This may seem outrageous, "Books need leather? Why would they in real life?" Well, I suppose that the real life explanation is that they have a nice leather cover, and should have required it AGES ago. However, the real explanation is that in the new Snapshot, you can make CUSTOM BOOKS! :O
They require a feather, a book, and an ink sac to create. The leather added to a book's recipe is to make the custom books a little more valuable.
To find out where you can play the Snapshot, Google "MineCraft Snapshot 12W17A", or do the same on YouTube. For a speedier way that won't last long, go to the MineCraft Forums; it will be on the frontpage for a while!