To make a Christmas tree out of books, you'll need a collection of books with different sizes and shapes, and some craft supplies. First, arrange the books in the shape of a Christmas tree, starting with the largest ones at the bottom and working your way up to the smallest ones at the top. Then, use a hot glue gun to attach the books together and add some decorations such as small ornaments, garlands, or lights to make the tree festive and colorful. Finally, top the tree with a star or angel made out of a book cover or paper.