This is the first book in Fearns rare Clay Drew series of Mars books, (4 book series), which is a fine and fun pastiche of Edgar Rice Burroughs John Carter of Mars books.
Used availability for John Russell Fearn's Emperor of Mars
October 1995 : USA Paperback
June 2015 : UK Kindle edition
Title: Emperor of Mars: Clayton Drew Book 1 (The Clayton Drew Series)
Author(s): John Russell Fearn
Availability: Amazon UK