The First Glance of your website or book cover is designed to entice the reader to pause and Look Inside! You want the reader be totally engaged in the experience of your book/website/persona. The direct TO BUY link means there's no wandering past displays of other books as you are going in or out of the store. Online retailers are NOT trying to distract you from your primary purchase with those scrolling sidebars and horizontal displays. Your purchase of that one book is encouraged, and when you look inside, that is all you see. That book.
When you return to that initial page either to buy, or read reviews, now you are even more aware of the: "Others who also bought this book, Bought these." Those excess book covers are to perk your interest in shopping more and meeting the free shipping price point of the bookseller. Some of those book covers are paid ads, like storefront positions, others are determined on your purchase pattern for customer satisfaction. This is the computer generated process to mirror a book seller recommendation.
While there are a lot of studies and theories, there's no crystal ball, or computer code assurance regarding the fate or success of your novel. Online retailers will continue to search for ways to encourage impulse buys but the bottom line today is: Readers only know when they FEEL they've read a good story, and are desperate to talk about it with others, so they spread the news with enthusiasm. Once you've written THAT Story is when you focus on getting seen with bright and clear marketing and that direct TO BUY link.
However, remember that impulse buys are no longer limited to wandering around a bookstore, either physically or online. They can happen with a point-n-click on many devises and apps. One of your book covers or blurbs could be included in a random selection process at any time, and a purchase can now be made anywhere.
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