Well, to be frank--I wouldn't want the novelization for my film to come out until at least after the opening week--and here's why: You can't trust the person at the bookstore to buy the book, and read it front-to-back.
You pick up a book, you can skim ahead to the end. You can skim through the book, and pick up vital information. In a theater, you see it front-to-back, and can't skim ahead.
Thus, unless the novelization is packaged, the suspense of a film could be injured by would-be-viewers in the bookstore.
But that's just me....