I think it's difficult to determine value. It's all about what you like. Depending on what the dust jacket looks like some of them can look really nice signed. Just the other day I was at a book signing by Hugh Hefner and he refused to sign the dust jacket. The jacket has a real dark area and would have looked cool signed in silver. Also, protecting the signature on a dust jacket could be more difficult.

Happy Collecting!!
Chappy

i getting my book sign next week but my question is i got a hard cover book and it also comes wrap with a book jacket, and since its really hard to frame a book and also no one can really see the autogragh couse most of the author sign inside i want to know if is just better to get it sign on the book jacket (it will also be easyer to hang couse its thin) or get in it inside..now like i say, i do not sell my autogragh but if i ever do so, whare would it be more valueble??