Alexei Panshin isn’t an author or critic with whom I have much patience. But once upon a long time ago, he wrote tales both humorous and deep of a remittance man named Anthony Villiers and his alien friend Torve, traveling through the Galactic Empire and committing the odd act of derring-do.
Star Well, The Thurb Revolution, and Masque World were out of print for many years, and alas, Panshin did not continue the series to its conclusion. (First, because his publisher did not want a fourth book; second, because he claims he is no longer the same young man who wrote about Anthony Villiers.)
However, an omnibus edition of the books came out in 2003 (which I didn’t know), and said omnibus is currently available on Kindle for the discriminating reader, for less than two dollars a book. Thus, you will not have to attempt to obtain them by crawling through many an obscure used bookstore, interfering with illegal gambling operations or Lovecraftian rituals of summoning by disturbing their dusty peace.
However, for whatever bizarre reason, Amazon will not let you buy this Kindle book unless you have accepted the odious 1-Click system, which I shall never do. So feel free to send Amazon a nasty letter about their stupid prejudice against normal buying methods. Apparently they must have shifted their policy within the last month or so, because previously I had no trouble buying Kindle/Mobipocket books from them. Twits.
Fortunately, Fictionwise also sells it as an ebook in several formats, including Mobipocket, which would take care of your needs nicely. The price is a tad higher unless you’re in their ebook club, though.