> How would a worm eat perpendicular to the pages and go from the first page of volume 1 to the last page of volume 2?

Sorry, what is the question supposed to be? You're positing a contradiction between two facts:

- The worm's path is perpendicular to the pages.

- The worm's path begins at the first page of volume 1, and ends at the final page of volume 2.

What's the contradiction?

The bookworm could have moved right to left from volume 1 to volume 2. Assuming the spines are facing out, the books are right-way up, and volume 2 is on the left of volume 1, then the answer would be 44mm.

While the answer does assume that V1 is on the left, there's no contradiction in your statement. If V2 happened to be on the left, it would still be perfectly logical for "a worm eat perpendicular to the pages and go from the first page of volume 1 to the last page of volume 2." They would simply have to go through more pages.