Everyone else has said it, but I just want to put my two cents of agreement in -

If you're in the middle of the book, drop it and never pick it up again. I own something like fourteen of them, including the Visual Guide. I consider myself a less intelligent person for reading all the ones I bought and the few I didn't. The Apprentice Adept series was okay, I especially liked the Game, and Immortality series was alright too. Piers Anthony's better stuff is his really early Sci-Fi. Most of it is out of print now, but you can find at used book stores. I don't recall any of the names, my father used to give me his old books to read. There was one called 'Ring' or 'Ringworld', about physically marking criminals, and there's another one set far in the future about preserving the last few true people of race, because everyone had lost their ethnicity due to inbreeding and become sort of 'muddy brown'. Those are alright, but as far as Xanth goes, there's more cheese there than in your local grocery store.