No. Some are richly designed to showcase the book contents and others are not. That’s the entire point! It’s not the books with fancy covers that are always the best. You could find a plain cover copy of The Hobbit in your local library next to another copy that is oversized with a gold-embossed cover and an amazing painting showing the party of 14 plus a Wizard huddled on a mountaintop against the storm…

…and they’re still the same book.