Literate Larvae?

I'm not 100% sure I've ever seen Book worms in action.  I suspect I have, and forgotten.  This one was evidently a keen devourer of Westerns by  J. T. Edson, who was so blinking prolific I'm not sure I've read all his stuff even yet.

Try as I might I can't find the entrance, which is NOT surprising as it would enter as an egg of virtually zero size, comparatively squeaking.

However - much more odd is the fact that I can find NO exit hole the same diameter as it's burrow.
On the left - Top & Bottom of the book looked alike, and "un-holed" ( I was tempted to say "unholey"  ;¬ )  but didn't.)
On the right - Burrows, quite literally from cover to cover, the little beggar must have wanted to see if the Baddies got their comeuppance in the end?