 Piers Anthony is a very prolific and very well-known, but mediocre author that I would rarely recommend But in this case you should pick up Prostho Plus It's about a dentist who arrives at his office one morning to find it occupied by a group of aliens who demand Some emergency dental work and they are so pleased with the results that they simply Take him into space with him and he spends the rest of the book Being traded from one Starship to another as a valuable commodity It is very original very entertaining and very funny