omnibus of: MOON OF THREE RINGS (1966) + EXILES OF THE STARS (1971)

For a good plot summary/set-up and some commentary on Norton, I rely on P. Schuyler Miller, and use excerpts from his review in Analog (June 1967):

"But Moon of Three Rings is not only the story of why it is that Krip Vorlund has taken refuge in the body of an animal, or how he is going to find his kidnapped body and return to it. Even for an Andre Norton story, there are almost as many interwoven plots as in one of A. E. Van Vogt's most intricate tangles. The difference is that they make sense. One of the feudal princelings of Yiktor has a very practical reason for wanting to capture a Free Trader and pry out of him information that will give him the same advantages and powers the off-worlders enjoy. Maelen, one of an ancient race who were the hill-folk of Yiktor long before Earthmen found it has a mission of her own. Her people, the remaining Thassa, have their traditions and their motives.

This is one of the stories which Andre Norton embroiders the theme of symbiosis between men and animals in the far future. The Thassa can link themselves telepathically with the intelligent animals who take part in their tent shows and in whose bodies they live and run in exchange. Like T. H. White's Merlin… the Thassa know that to be an animal is a vital educational tool." [P. Schuyler Miller]

Exiles of the Stars - the sequel to Moon of Three Rings. As crew members of the Free Trader ship Lydis, Maelen, in the furred body of Vors, and Krip Vorlund, who now walked as a Thassa, had put down on the planet Thoth to find themselves in the midst of an explosive civil war. The Thothian priests wanted them to transport the valuable Forerunner treasure to Ptah for safekeeping. The Free Traders agreed. But shortly after lift-off, disaster struck - and their ship was forced down on the uninhabited, terror-filled planet of Sekhmet.