The Ruby Tools are a set of tools that, while being enchanted, can boost its level beyond the vanilla maximum enchantment count by 1 (Like Efficiency 6 and Fortune 4). It can boost up to three times, on separate or singular enchantments. For example, if your pickaxe is boosted twice on Efficiency 4, it will bump its effect to Efficiency 6. This extends to Silk Touch. Unlike Amethyst Tools, enchanted books do work on the Ruby Tools.