So far I like what Pretending, acw, and matahari wrote. Otherwize's post is a candidate for most hypocritical of the year in that it practices the opposite ethics of what is being preached, kind of like the priests who jack off to lolita websites.
In the case of most books I would do A - nothing, because they have my money and by making a bet I am giving them a free chance to do whatever they want with it. They could wait until the game is over and cancel it if it wins but honor it if it loses. I don't want to give them such an option against me so I just stay away. If the book has been especially good to me I may choose D but that would be an exception.