1960s Ace double novel: The Caves of Mars by Emil Petaja

The Caves of Mars (1965), a novel by Emil Petaja

At left: Paperback original (New York: Ace Books, 1965), 125 p., #M-133, 45¢. Cover by artist Alex Schomburg. An Ace double novel, bound with Space Mercenaries by A. Bertram Chandler.

Here is the blurb from inside the front cover:

Ric Coltor had lost an arm in an interplanetary exploration. For a spaceman at any other time, that would have meant the end of his career. But not with the marvelous Martian Panacea in existence. Extracted from a fungus found only on the Red Planet, it promised mankind perfect health and longer life, for it grew back internal organs, conquered disease, and could even grow back arms. ...
gave its users glowing good health, but it also gave them a fanatical devotion to the man who administered it, Dr. Morton Krill. A devotion that was so all-encompassing that any man who received it could easily become dictator of two planets if he were twisted enough to desire that. Dr. Krill was!

In his The Ultimate Guide to Science Fiction (1990), David Pringle called The Caves of Mars “an ill-written, low-pressure space opera.”

Surprisingly, noted SF&F critic Rich Horton has not reviewed Petaja's The Caves of Mars.

Equally surprising: You can read the first 30 pages of The Caves of Mars online!