A few nice book images I found:

Burroughs, Edgar Rice – The Gods of Mars (1981 PB)

Image by sdobie
The Gods of Mars by Edgar Rice Burroughs
Ballantine/Del Rey, Seventieth US Printing, November 1981
190 pages
Cover art by Michael Whelan

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2015-04-15: 1000 views
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2015-08-06: 3000 views
2015-10-08: 4000 views
2015-11-26: 5000 views

Witchcraft #5 (1953) by Frank Kelly Freas

Image by Tom Simpson