Thought you got the shelf wear from moving the books in & out of the shelf,having them stored on the edges as well as the fact the hard covers are slightly larger than the actual page of the book so you have the weight of the pages bearing down on the bottom of the book. Then you have this weight having a tendency to pull pages away from the spine as well. Well,thats what i always thought
Just had a quick think & a look,i came up with this on fleabay. Providing its sturdy enough i think this could actually work to store you books in & display them
http://www.ebay.com.au/itm/12x12-SCR...item3a8393cdf8