Leigh Brackett 
Black Amazon of Mars [EPUB ebook] 

Female author Leigh Brackett was the Queen of Space Opera! In this thrilling tale, carrying out the last wishes of a comrade, mercenary Eric John Stark takes on the task of returning a stolen talisman to a walled city near the Martian pole. Now all he has to do is get past the brutal clans of Mekh and the shadowy Lord Ciaran to get to where they’ll probably attempt to kill him. All the while he tries to hold on to the talisman with special powers. That’s not easy for a mere human.