Half of Amazon book sales are planned purchases, according to Forbes–meaning that by the time people get to Amazon, they already know what they intend to buy.
This statistic doesn’t surprise me; it backs up what common sense indicates–that people visit websites with a mission. Not many readers “browse” online retailers looking for suggestions the way they might browse shelves in a bookstore. By the time they get to Amazon, they likely have titles written on a post-it note, gleaned from some other source (word of mouth referrals, Goodreads, book reviews in newspapers, magazines, or blogs).