So I have been looking into Tarbell's books and I found two (sort of) books. The first is 'The original Tarbell lessons in magic' and the other one is 'The Tarbell course in magic' which actually consists of eight books. Is there anyone who can tell me what the difference is? 'The original Tarbell lessons in magic' seems to be the one that Tarbell wrote originally in the 1920s. But what is the other eight books?