Dust jackets do in fact protect books, if not actually from dust: A dust jacket guards against scratches, scuffs, jelly, and other distortions unworthy of a book's perfection.
When talking of first editions, a true first edition is only so when its Dust Jacket is present (if originally issed with one).
Many 20th century books not yet to great extreme in golf books, but in modern firsts command high premiums, for example Casino Royal, Ian Flemings first book without a Jacket £2500.00 with £60,000.00 there are many other similar examples.
A golf book collector still has the opertunity to add jackets for relatively small amounts over the value of a first without a jacket. From a scarcity view, wre- 1940 Jackets are scarce and desirable.
Sometimes a later dust jacket is paired with a first edition book to add value, this we do not believe a correct practice, if not disclosed in the books sales details, otherwise it is a type of forgey!
If the book has spent its life with its Jacket, expect the book to be in a very good condition.
Torn or chipped Jackets often give the wrong impression that the book to is in a poor state, this is usually the oposite and a chipped Jacket is still more disirable than No Jacket.