Despite the advice- Never judge a book by its cover; we get attracted and pick books randomly due to its attractive cover. So book covers are substantial! Period!
A book cover is a protective layer within which the pages of any book are bound together. This covering can be made of various materials such as paper, hard-paper boards, or plastic. Additionally, hardcover books may come with a dust jacket for added protection.
Did you know that during the middle-ages, front book-cover designs were incredibly ornate? They often featured jewels, pearls, and gold. In the 20th century, it changed from gold-stamped cloth/leather covers to dust jackets.Today, with the advancement of technology and out-of-the-box thinking of a book design company, we see bright colours, bold fonts, and different styles immerging on book-covers.Book-covers are great marketing tools as well. Book covers are crucial even if you convert book to e-book. They generally have these common features, which lures one to pick it up to read it.
Some more facts about book-cover design are-
Source: https://bookcoverdesignersuk.mystrikingly.com/blog/facts-about-book-covers-which-you-may-not-know