I pick up old books mostly at thrift stores and garage sales for under $1.00. I collected a selection that I liked and stacked three or four of them on the kitchen counter to see if they all "went" together. Then I measured the width of the book and cut mounting tape accordingly, taped it to the back of the book and secured the next page over the tape forming a 'pocket' for the L-brackets to fit. Make sure you tape at the furthest end of the page.
Then stack the rest of the books on top and decorate! Ta Da!!
Hope I made the instructions clear enough for you--if you have any questions, feel free to email me. Also, if any of you do this, I'd LOVE to see your pics!!