I maintain that one should remove the dust jacket and then read the book. This keeps the dust jacket looking nice and therefore the book will look nice and brand-new on our bookshelves. He thinks that the dust jacket should stay on thereby keeping the actual book in excellent condition. I don't see why it should matter so much what a book looks like when it's HIDDEN BY THE DUST JACKET. Make no mistake: I hope the book underneath still looks like new too. Still, I'd much rather see a pristine-looking dust jacket covering a slightly dirty book than a crumpled and torn dust jacket hiding a perfect book.
So we each read hardcover books the way we think it should be done. This is not usually much of a problem as our reading selections rarely overlap --- like Scotty in "Star Trek" my husband reads mostly "technical manuals" relating to his work as a CPA. I am the one who reads lots of books. But when he reads one of my books WITH the dust jacket on...ugh.
Full disclosure about me: I like my books to look brand-new for as long as they can. The books I read several times, generally the paperbacks, eventually get the look of a well-loved book and I don't mind that. I know many people even prefer their books to look used because it shows how much the books are loved.
I have belonged to an online used book club for a couple of years and I have received books in almost all conditions from "perfect" to "disgusting" and have learned that one person's "great condition" is another person's "that's not even coming into the house" (mainly the ones reeking --- to me --- of cigarette smoke). I am fine with reading these used books and then sending them on to the next reader.So I have to say that I am getting better about reading "well-loved" books.
But if it's a book I want to keep on my shelves, well then it better look brand new!