A set of sub-types under the Hardcover format to differentiate what kind of hardcover it is. For example:

(a) Case Laminate (Hardcovers without dust jackets, cover art is printed directly on the covers)

(b) Dust Jacket (Hardcovers with dust jackets, no cover art is printed on cover)

(c) Jacketed Case Laminate (Hardcovers with dust covers, and have more art printed on the cover)

This would be useful for both people like me who tend to avoid hardcovers with dust jackets due to being afraid of damaging them, and people who prefer books with dust jackets because they are really cool to the strong of will.

I don't usually collect paperbacks so I don't know much about the different types of those books, so this could be potentially used for paperbacks as well if they have any special distinction.