Update: The Bio of a Space Tyrant series has apparently been re-released, and is available at Amazon.com. The new version is quite expensive, though, so I would suggest buying a used copy instead if there is one available.
I have read a bunch of books by Piers Anthony. Of all of them, the ones that I would most recommend are the Bio of a Space Tyrant series and the Incarnations of Immortality series. Sadly, as far as I can tell, the entire Bio of a Space Tyrant series is no longer in print. The links to four of the five books below are all to out-of-print books that Amazon.com will try to find in used book stores. The same goes for the link to the whole series. They didn't even list Politician at all that I could find (see update above -- the series appears to be back in print, but the new versions are expensive). I was truly distressed to find that some of what I consider to be Anthony's best work is out of print, while all of the Xanth novels seem to be going strong. In fact, many of his best works are out of print. Apparently, people who would read his good stuff encounter Xanth first, and figure he has no talent, and the people who do buy the Xanth novels don't care for serious books. On the bright side, all of the Incarnations of Immortality are still available. The first number of Xanth novels I read were fun, but they went downhill after that. I stopped after Harpy Time because I just didn't like it, and didn't want to read another book like it. I enjoyed the Apprentice Adept series, as well as the Battle Circle trilogy. I liked the Kelvin of Rud series, the Mode trilogy, and a number of his non series books. But I have to say that many of the books I liked the best were the ones he wrote earlier in his career. In his more recent books, he seems to be trying to preach so hard that his writing is suffering for it. I don't mind an author presenting his point of view on a subject, or even trying to get others to see it the same way, but when it makes his writing significantly less enjoyable, I'm not going to bother.
Books I've Read by Piers
Anthony