Harry Lorayne is a well-known magician and mentalist, and his book "The Magic of Harry Lorayne" (not specifically "Mathematical Wizardry") is a classic in the magic community. However, I found that Harry Lorayne did write a book called "Harry Lorayne's Memory & Mental Magic" and also "Math Doku" and some mathematical puzzle books.
You're looking for a resource on mathematical wizardry by Harry Lorayne! Harry Lorayne Mathematical Wizardry Pdf Download