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 l

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.