My youngest loves coloring books, but it is difficult for her to find uncolored pages in the bound books after a while. I took my heavy duty guillotine paper cutter and cut off the spine of the coloring book, freeing the pages so they could be sorted into colored and uncolored.

My youngest was pleasantly surprised with the fresh stack of ready-to-color sheets, and I was pleased with how fast and clean the cutter worked. Tearing sheets out of a book is often messy and frustrating. By cutting a 1/4 inch off the spine, the pages are freed from the glue easily.
Once my concept was proved, my youngest agreed to let me process the rest of the books. Any book that only had one or two colored pages I left alone, but the books that were mostly colored were cut and sorted.

I now also have a stack of colored sheets that can be displayed and scanned easily for posterity.