We’re often taught not to judge a book by its cover. After all, you never know what beauty and magic could be hidden within. But this doesn’t stop people from doing so anyway. When it comes to the human beings we meet or the actual, literal books we encounter in shops, on shelves or online.

One survey found that 57% of Americans buy books (and 80% avoid books) solely based on their covers. And therefore, bad cover design is one of the most common reasons for low book sales.

“​​Humans are visual creatures,” explains best-selling author Tucker Max. “We see our way through the world, and vision is our defining sense. Humans can be immediately reached, engaged, and moved by color and shape because these images enter the brain literally at light speed. This is the power of design.”

Max says that book covers exist to give visual form to written content. “A great cover makes someone in your intended audience say ‘I need to read that,’ by showing them why the book matters to them in a way they can immediately grasp (or at least raising their interest enough to want to learn more). It should help your audience realize that they should be reading your book.”

However, some argue that the cover isn’t the first, or only, thing someone judges before buying a book. Writing Cooperative notes that nowadays, books aren’t only bought in physical stores anymore.

“Most books are now discovered either by in-person word of mouth or online, and in both cases, what is the first piece of information they receive? The title,” reads their site.

The experts say while a good title won’t necessarily ensure your book flies off the shelves, a bad title "will almost certainly prevent it from doing well." As the Cooperative puts it, many potential readers stop considering buying the book once they have heard the title, and nothing else.

A study published in the Journal of Retailing and Consumer Services found that around a third of books are bought as gifts, women buy and read more books than men, and that higher-educated and older consumers tend to read and buy more books.

The same study found when deciding on whether to buy a book, the top factors noted by those surveyed were the "Title”, "Synopsis”, “Subject covered in book”, “Recommendation of family and friends” and “Books with discount/on sale”.

According to the Writing Cooperative, "almost every potential reader will judge whether or not to buy and read your book before they have read one single word inside the book."

They also say that often, readers aren't even aware of their thought process when browsing a book store. But that it takes less than a minute for someone to give the book a thumbs up or a big fat "no" before they either head to the till to pay or put the book down and move on.

"These buying decisions are a series of instantaneous and mostly unconscious judgments. They are made in less than 60 seconds, and they are made together, each influencing the other, not individually," notes the site. "These judgments are real and substantive; in most cases, they are the main evaluation and purchase triggers."