Podkayne of Mars

Podkayne of Mars by Robert Heinlein. 

Top: Berkley, 1970. Cover uncredited.

Bottom: Berkley, 1971. Cover uncredited.

There's probably about 40 covers for this book but I enjoy the juxtaposition here of what one might expect of this story depending on which cover they saw.

The Last Defender of Camelot

The Last Defender of Camelot by Roger Zelazny. Pocket, 1980. Cover: Carl Lundgren

Ringworld

Ringworld by Larry Niven. Ballantine, 1976. Cover: Rick Sternbach