Piers Anthony is an author best known for his Xanth series. To say he was a prolific writer would be an understatement. While he had several short stories published in his early years, he really didn't start publishing books until the mid to late 1960s. He has over 130 books published which equates to nearly 4 books per year for the past several decades. Now obviously he didn't produce works like that consistently, and he probably had numerous manuscripts and story ideas in various stages of completion prior to becoming famous. Regardless, you can't argue with numbers - that's a lot of writing.
Many will tell you that Piers Anthony's early works were his best. This is mostly true; however you will find dozens of great books written throughout his career. His focus changed from an amazing blend of science fiction and fantasy to something that was seemly overrun with sex and puns. As far as his multiple series go, he just takes an idea and runs with it - often much too far. The first three books in any of his trilogies are typically better than the last three. (Don't argue about the number of books in a science fiction trilogy. Douglas Adams has similar problems with math.) It seems that as he grew older, he began catering to a younger audience even though, at times, his subject matter did not. This was a slow decline which can be unnoticeable if you are already immersed in his books. It's only after you have some other authors under your belt and you pick up one of his novels years later that you ask yourself, "How did I ever read this?"
Again, this is not to say the man does not possess any talent because he certainly does. He has a huge fan base from all demographics. While I do not know if he still has this policy, he used to personally answer every piece of fan mail that he received. Most of his books (especially those in the Xanth series) would contain very long authors notes, sometimes spanning 30 pages or more, telling his readers about his life and experiences while writing the book. These notes would also thank readers by name that had sent him ideas that he had incorporated into the book. Sometimes there would even be sneak previews of his upcoming books. Many readers would read these just as intently as the novels themselves.
Pen Names of Piers Anthony Dillingham Jacob
Piers A. Jacob