Tales of the Galactic Midway — Michael D. Resnick

Out of print for several years, Farthest Star SF has brought all four novels in the series back in one fantastic omnibus edition! Thaddeus Flint knew the carny game better than anyone. He could con the marks until they practically begged him to take their money. But suddenly he was losing business as everyone flocked to a new traveling circus, one whose freaks were the real thing -- no makeup, padding, or phony scales! So he stole them and got much more than he bargained for! They weren't human "freaks" but honest to goodness aliens from all over the galaxy.