We are often asked, “Do Bookplates Devalue Books?” The answer is it depends. The majority of the time, ownership bookplates (ex libris) do devalue books. There may be some exceptions in regards to ownership bookplates, but there would be few, if any. I wouldn’t pass up a great deal on a used book because of a bookplate, because it doesn’t change the books readability. It does have an effect on the resale value though.
What about author signed bookplates? A book that includes an author signed bookplate may have more collecting value than one without, but it will still not be as valuable as one in which the author has signed his or her name directly. Let’s be fair, the author signed the bookplate, not the book.
So, should you affix ownership bookplates to your books? We don’t recommend it on high quality, expensive books simply because it affects the value of the book if you ever wanted to sell it. If you are wanting to affix the bookplate on a dog eared mass market copy of your favorite books, by all means go for it.