"Historically, dust jackets are a new concern for authors; you don't see them much before the 1920s. And dust jacket is a strange name for this contrivance, as if books had anything to fear from dust." ― Paul Collins, Sixpence House: Lost in a Town of Books
A college roommate of mine removed the dust jackets from his books and threw them away as soon as he bought them. Other people find dust jackets a nuisance as well. Peter Robins writing for the Guardian books blog on February 25, 2010, asked “What is the point of dustjackets?” He concluded in his piece “No dustjackets required” that the dust jacket “remains an unnecessary and vulnerable encumbrance.”
That might be true of some books—a dust jacket is unnecessary for most leather bound books, books with decorative cloth bindings and books with pictorial covers. Accordingly, most of these are published without a dust jacket. For a book which is published with a dust jacket, however, the dust jacket is necessary and while it may be vulnerable it is not an encumbrance.
A dust jacket serves several important functions, but it is more than just functional. It is an integral part of the book. A book without its dust jacket is incomplete. Yes, you can still read it and enjoy it, but you do not hold in your hand the final result of the artistic process that culminated in the book.
In the small city where I live there is a sculpture which when first installed had colored sailcloth on it. The cloth wore out many years ago, and no one has ever replaced it. Without the sailcloth the sculpture is not the same as it was before. Nor does it now convey what the artist wanted it to convey. Every art object—and a book is an art object among other things—is incomplete and damaged if any part of it is missing. Book collectors, like art collectors, want the whole work of art. They want the whole book, and that includes the dust jacket.
The dust jacket serves other purposes. It provides the first interpretation of the book. The jacket designer is in some way the book's first critic. A well designed dust jacket also serves to attract a reader browsing in a store. If a book catches a browser's eye, he or she can then turn to the dust jacket's back and flaps to find information about the author and a synopsis of the book. A good dust jacket helps sell a book.
Dust jackets provide the vast majority of books published today with their only color and art. Without their jackets, most books are visually dull. Dust jackets are so important that sometimes an essentially worthless book can be valuable because of its dust jacket. There are poorly written books which have beautiful dust jackets and are collectible solely because of the jacket. Most art deco book jackets are fabulous even if the book under the wrappers is not worth reading. A copy of Irma Rombauer's The Joy of Cooking in its original 1931 art deco dust jacket is worth owning even if you never eat at home.
The jacket does have a functional purpose; unfortunately it is limited. It is not even a great protector against dust as it does not protect the top edges of a book. It does, however, protect the book against wear. The wear you see on a dust jacket is the wear you would see on a book's covers if it did not have a jacket. The modern glossy dust jacket seems to protect books better than the older ones. A coffee spill is more likely to run off a glossy dust jacket than a matte one. By using a mild cleaning solution on a damp cloth, or better yet a solution designed for the purpose sold by companies like Brodart, it is often possible to clean coffee cup and soda can circles, other drink and food stains and the remnants of price stickers from a glossy dust jacket without damaging it. If these same stains were on the book's cover, they would be virtually impossible to remove. Brodart and other companies also sell supplies that will clean the grime from a dust jacket with a matte finish.
Since dust jackets are an integral part of the book, it is a good idea to protect the dust jacket as well as the book in order to protect your investment. You can protect a dust jacket by purchasing mylar covers designed specifically to protect dust jackets. Mylar covers are replaceable when they wear out. Dust jackets are not.
Most booksellers do not buy a book if its dust jacket is missing unless it is a rare book. That means when you remove the jacket from the typical run-of-the-mill book, you have reduced its value to zero. A missing dust jacket will reduce the value of a collectible book by 75-90%. That's reason alone for keeping and protecting a book's dust jacket.