What does the note at the beginning of the book say, and what does the book store clerk give the authors? What is the authors' response?

The book begins with a typed note to the reader, stating the long-term interest of the writer Holly Black, and the illustrator Tony DiTerlizzi in faeries. At a book signing, they are told that there is a letter for them from the Grace children. They pass a note back to the bookstore clerk, who assures them it will get to the Graces.