Did you already buy the books online somewhere else?  Do you want the bookmarks and the book signed?  Well, here's a way to get a signature plate and a book-specific bookmark for all 4 books.

Signature plates are essentially stickers with the author's signature.  They use acid-free paper and adhesive that won't damage your book over time.  The signature is done with archival ink so it shouldn't fade or discolor over time.