That's a new item's type in Alpha 3.5x. You may need to do something to gain one and by using it, lear a news crafting recipe.
“Learn to craft the Enhanced Iron Sword with the Iron Sword, Carbon Steel Bar, and Animal...Enhanced Iron Sword Book
“Learn to craft an Umbrella with Spine, Copper Bars, and Fiber Cloth. Since the Alpha 3.5x, it is...Book Umbrella