Step 2: First Cuts
Working from one cover to the next, slice along the seam of the end pages with the exacto knife.
Once you have sliced the end pages apart from each other you should be able to see or feel some strings holding together the text blocks. On one side of the book (i.e front) cut the strings. If you want to save all of the pages be really careful. Otherwise you should be able to easily cut through the strings. On the other side of the book pull out the strings. This will create a nice clean break between the text block and the covers.