Step 1. Hold both sides of a wire hanger in your hands, and bend inwardly.
Step 2. Flatten each end of the wire hanger  with pliers.
Step 3. Make a 90 degree bend, about 2-3cm from each end, holding the wire hanger.
Step 4. Make a bend again for both sides, estimating room for a book in the holder.
Step 5. Hold the twisted central portion of the hanger with pliers supporting the rest part, with the palm of your hand, and make a 90 degree bend.
Step 6. Twist the hook to face the book holding portion.
Step 7. Bend the end of the hook into a small hook.
Step 8. Hook the hanger bottom part to the small hook.
Step 9. Tighten the end of the small hook inward again.