While acknowledging that we can’t judge books by their covers, how much does the design of a book affect your reading enjoyment? Hardcover vs. softcover? Trade paperback vs. mass market paperback? Font? Illustrations? Etc.?
The design of the book can affect my enjoyment of a particular book, but won't always. Certain books need to be hardcover or softcover, but there's not always a rhyme or reason as to why. Mostly I don't like hardcover books, but that is because I cannot stand bookjackets. And as such I will generally get rid of a books bookjacket if I get it in hardback. I like classics to be hardbacks (sans bookjacket). It makes them seem older, more valuable and important. And Harry Potter books. I'll only own those in hard back. And coffee table books. Everything else comes in paperback.
Also, I very much need my books to match. And by that I mean if they're books by one certain author or a series of books, they all need to match. Have the same style of cover, come from the same publisher, be of the same set, whatever. They need to match.