Letter Head (solution)

by Patrick Blindauer

The left column of clues is missing its first letters:

The missing letters spell MOBY DICK, FOR ONE, which is a clue for BOOK (or is it NOVEL or WHALE?).

The right column of clues are categories, each of which can be filled by adding a letter to an answer from the first group:

The added letters spell VIRTUAL PRODUCT. This, taken with BOOK, clues the final answer, EBOOK.