They say don't judge a book by its cover cause that's not the most important thing about it, it's the content. However, the aspect of the book matters for various reasons. For starters, it can draw your attention in a book store and make you read the description on the back or read its first chapter and make you want to buy it. That's pretty important in the package design business. And then, considering that you spend some time reading a book, you'll see its cover over and over again when you close it and having a nice cover would make you feel pretty pleased, besides the interesting content that you have just read.