John Matthews has produced a number of successful divinatory systems based on early spiritual beliefs - including the best-selling Arthurian Tarot (with Caitlin Matthews and Miranda Gray), The Wildwood Tarot (with Mark Ryan and Will Worthington), The Green Man Tree Oracle (with Will Worthington), The Celtic Animal Oracle and Grail Tarot (with Giovanni Casselli). His book, Pirates, was No 1 in the New York Times Book Review and a bestseller for 22 weeks in 2007.