If you’d like to read this terrific series there are several ways to do it. They were reprinted in pulp magazines during the 1940’s and early 1950’s and free copies of these can be found online.
“Polaris of the Snows” was reprinted in its entirety in Famous Fantastic Mysteries Combined with Fantastic Novels Magazine, July 1942 issue.
“Minos of Sardanes” was reprinted in its entirety in Fantastic Novels Magazine, November 1949 issue.
“Polaris and the Goddess Glorian” was reprinted in its entirety in Fantastic Novels Magazine, September 1950 issue.
Altus Press also published the three books as a complete omnibus which can be ordered directly from lulu.com as a Print on Demand book. I didn’t want to recommend it until I’d received my own copy and it has arrived today. The volume looks great and it will be nice to have a clean new copy of the story. Be aware though that the reprint omnibus lacks the original illustrations.