Method 1

1. Gather rectangular pieces of paper of the size you want. You will need an even number of them. If you want to make one from recycled or one-sided paper, glue wrong sides together first, so that all the pages are empty. To make a book with papers that already have writing on them, arrange them so that when you fold in half, they fall in the correct order.
2. Take a set of no more than 8 papers and fold the whole set in half. If the set is too bulky, reduce the number of sheets in it. This is called a "signature."
3. Make more such signatures until you have as many as you want for your book. A single signature book will be enough for some projects.
4. Poke a hole in the middle of the crease of each signature, as well as one on either side (about 1 inch from the edges). For smaller books, you can simply make only two holes.
5. Using thick twine, sew the signature together and tie off in the middle. To do this, start from the inside middle, come back in through the top hole, go out through the bottom hole, and come back in the middle and tie a big knot. If you don't want to sew, poke twine or yarn through the holes from the outside and tie inside. You could also glue the spines of each sheet together, but be careful not to let the glue spread (a thin glue stick or brush can work well).
6. Cut off unneeded ends of string or let each signature dry. Do all the signatures for the book.
7. Cut 2 sheets of cardboard 1/2 inch bigger on 3 sides than each half-sheet of paper. Cut a piece of cardboard the same height and as wide as the thickness of the book. Cut some decorative or black paper or fabric the same height plus 1 inch, making it as wide as the thickness of all the signatures plus an inch. This extra piece will make the spine of the book.
8. Cover the cardboard or paint and decorate.* Glue the small piece of cardboard to the spine paper or fabric. Fold over the extra at top and bottom and glue in place.
9. Glue the spine to the cardboard, smoothing it out with a round pen or pencil.
10. Glue the signatures into the spine. *If you want to sew the signatures to the cardboard, do so before gluing it to the spine (see * in 8.).
11. Let everything dry and your perfect book is done!

Method 2
1. To make a quick-and-easy book, gather sheets of paper all the same size for your book (or even different sizes, as long as they have one same-size edge).
2. Make 2 cardboard covers 1/2 inch wider than your book on 3 sides. Cover with wrapping paper, or paint or decorate.
3. Punch or poke 2 or 3 evenly-spaced holes in all sheets and covers, and line up.
4. Using decorative yarn, thread, or ribbon, tie all the sheets together through the holes, and tie off a bow in the front for a flourish.
5. Your book is ready to use. To add more sheets or reorder them, simply untie, restack, and tie together again.