Early Andre Norton fantasy about a gemstone

Andre Norton. The Zero Stone (1968). Morduc Jern inherits a ring with a strange home-seeking stone from his gem-dealer father. His master dies when a weird priesthood targets them both as potential sacrifices. And then one complication after another tangles the path of Murdoc and Eet, a mind-talking and -reading entity that commandeered the ship’s cat to produce a cat-like body for itself.
     They’re marooned on a planet that may have been colonised by the Old Ones, the stone behaves as no stone should, and so on. There’s double-crosses and hidden agendas and the Thieves Guild and such. Pretty good fantasy, but the plot is basically that of a role-playing game: hero must find his way to the prize. Which he does, and the denouement hints at future adventures of the intrepid pair.
     Norton writes well, so that most readers will likely read as I did, turning the pages to find out how Murdoc and Eet would escape whatever predicament they’re in, only to tumble into another one. Well done example of the genre. **½