Trimming a book that keeps growing back

I'm at my bench trimming a book block but every time the plough slices clean, the pages seal themselves up again like a wound that won't stay closed. My bone folder is warm from sunlight that isn't there, and someone keeps asking me to hurry, so I slow down out of spite. I wake up right as the thread starts to pull the whole thing together, and I'm honestly a little annoyed I didn't get to finish.