Answer: The bookworm will have gone 4 1/4 inches.Here's How: The first page of Volume 1 is on the right side of the book when the set is standing on the shelf, and the last page of Volume 4 is on the left side of the book. The worm eats his way through the cover of Volume 1 (1/8 inch), all of Volumes 2 and 3 (4 inches) and the back cover of Volume 4 (1/8 inch) for a grand total of 4 1/4 inches.