Minecraft wiki entry for Diamonds, associated text: After crafting the enchanting table, small enchantments are possible, but to get Fortune, let alone Fortune III — the table's power must be boosted with bookshelves. 15 bookshelves are needed, requiring 45 books, in turn requiring 45 leather, 135 paper, and 90 planks, so having a tree farm is handy. See the Enchanting article for details of how to arrange those.