According to this article in The Guardian newspaper
people usually make up their minds in between 10 and 20 seconds when buying a book.
It follows a list published by bookseller Abe Books listing 30 books "worth buying for the cover alone".
Interestingly The Guardian
's article says while a good cover can often help sell a paperback, sales of more expensive hardbacks are less affected by their design.
As a professional buyer, does the effect of marketing lose its effectiveness the more expensive a product gets?