I saw tons of how-to's on Instructables and other websites for this awesome way to store books. I altered it a bit for my own purposes, but I think it looks pretty much the same, and I didn't have to destroy a book (which all the how-to's I've read had suggested).
What you need:
-A hardcover book that you don't care about too much (I used one of my dad's old French text books and a book I bought at my local library sale for two dollars called "Cat Watching"..hilarious!)
-Other books to be put on the shelf (obviously)
-One U-bracket per invisible shelf (found these in my garage)
-Heavy duty screw
-A few butterfly clips
My soundtrack: CCR Greatest Hits (I cannot get enough!)
Find a stud where you want to set up the shelves. Mark where you want the U-brackets to be. Pre-drill holes.
I opted to use a basic screwdriver to install the U-brackets by hand. Make sure they're level.
Take the hardcover book and place it on the U-bracket, leaving the back cover and last page or so hanging underneath the bracket. Use a few dots of Elmer's glue to stick the back cover to the rest of the book, and clamp it shut with some butterfly clips. Once it dries, you can take the clips off. The stability of the shelf isn't reliant on the back cover being glued, so if it comes undone over time, just re-glue it and clamp it for a bit longer.
Stack your books on top of the hardcover base and voila! Invisible shelves!
Please leave some feedback in the comments and feel free to ask questions. Thanks for reading!