1. When collecting books, how can you verify a certificate of authenticity for a book signed by author? What should it look like and who issues it?

2. If a book is in new, never used condition what effect does a black mark made by a magic marker on the external edges of pages have on it's value?  i. e. With book closed the top or bottom of the book's pages is marked by a dot or completely blacked out with marker. Marking isn't visible when book is open.

1. The only way to be sure the author signed a book is to get it signed yourself. Beyond that, you need to buy the book from a reputable dealer that may be able to give you the book's provenance.

2. The mark you are referring to is called a remainder mark. This is done so the publisher can sell the book at a loss because it is "damaged". It does not really have an effect on condition, but must be mentioned in a description and will most likely lower it's value. They used to do the same thing with record albums by cutting a notch in the jacket. These were called "cut outs" and were sold in bargain bins.

Extremely helpful information above!

So, Thomcollects, are you saying that a bookseller intentionally marking books had to do with them being able to sell them and declare them as a loss for tax purposes or some other reason? If so, what are the possible reasons/benefits for doing this type of thing to a book, or other kind of merchandise, please?

Thanks!

It is actually done by the publisher from what I understand. I believe it allows them to write off the difference between the original wholesale price and the eventual wholesale price of a damaged book. I assume that there is some tax loophole for information media since I have only seen records, cassettes, books, and CD's marked as suchand sold at a loss. You will commonly see these items at dollar stores and closeout stores such as Big Lots, Ollies, C-Mart etc.