Thanks for the book, Harry! I've been wanting that New Theory of Numerology for ages!"
—Hermione Granger to Harry Potter.[src]
New Theory of Numerology, by Lukas Karuzos,[1] is a book that seems to be about Arithmancy, but is not a required text for the subject at Hogwarts School of Witchcraft and Wizardry. Harry Potter gave a copy to Hermione Granger for Christmas in 1995.