Minecraft wiki entry for Enchanting_mechanics, associated text: The space between the bookshelf and table, at the height of the bookshelf must be air (even a torch, snow cover or carpet blocks the effect). For corner bookshelves, the space between is 1 block diagonal from the enchanting table; for all other bookshelves, the gap must be to the side of the enchanting table. This is illustrated in the following diagrams (the white spaces are air, and the do not matter):