Choose books that go well together as they will be glued in a stacked position. My personal preference are books that look aged.
Use a ruler (or in my case, a piece of Lego. It works just as well :) and pencil to draw marker lines on the book. Decide how far or close you want to cut near the edge of the pages.
Using a knife, cut deeply along the lines leaving the boarder uncut.
Cut pages of the book completely out, only leaving the boarder you marked. Use the same dimensions and mark a boarder along the second book's front cover, as you will be removing that as well.
Once you've removed all pages from your books, you may place them on top of one another. Use glue to hold them in place.
Using generous amounts, brush glue along all the sides of the book pages inside and out.
Let sit until dry using a weight on top to hold the pages in place, allowing them to properly stock together. Re-apply glue if needed.
You may use fabric to line the inside of the empty books, adding a nice touch. I like the choppy-paper look so I chose not to glue any fabric inside.
There you have it! A funky box that at first glance, looks like a stack of books.