This method for creating invisible, wall-mounted bookshelves DOES NOT require damaging a book as part of the construction process. You can use any variation on the materials I have listed. The key is to use what you have around the house, if at all possible, and keep it cheap. Remember, it doesn't matter what the finished product looks like. No one will see it!
Step 1: Step One : Materials
I tried to use materials that could easily be found around the house. Most people will probably have to purchase the corner bracket, but they are easy to find at any hardware store and are very inexpensive.
2", 3' or 4" Corner Bracket
Wooden Paint stirring stick
Jumbo Paper Clip
Wire cutters or needle nose pliers