I read these as a teenager many years ago. They are pretty much Edgar Rice Burroughs John Carter of Mars series redone on Callisto. If you ever read of John Carter's exploits with Dejah Thoris, and if you enjoyed them, this is for you. Excellent young adult series with lots of action, aliens, sword fighting, and swashbuckling adventure.
good book in the Bouroughs tradition. first in a series of Jandar, Alien in a land of a thousand foes.
Front cover says: "The first fantasy in the saga of Jandar, alien in a land of a thousand foes."
For those who were/are fans of Edgar Rice Burrough's this is the perfect add on. Jandar of Callisto could be John Carter of Venus. As a young teen I devoured this series along with ERB's Mars stuff and loved it all. Great action adventure for young readers.