Schatje’s Shelves has a few old books, but there are certainly none that would be considered very rare or valuable. I do occasionally buy Folio Society books which may have some value in the distant future though I purchase them because the quality of the books makes them almost works of art.
I was therefore interested in a visual essay in The Telegraph on the world’s most expensive books: http://www.telegraph.co.uk/culture/books/10475282/The-worlds-most-expensive-books.html?frame=2746338. I was familiar with the Gutenburg Bible and Shakespeare’s First Folio, but I was surprised to learn that a J. K. Rowling book has the record for a modern literary manuscript and a children's book.
Schatje’s Shelves always has room for donations of any of these!