I'd say sneak attack, with gas? It's obviously Earth. Everyone's dead, although the lass on the left seems to have perished while leaning.
The book was a collection of serialzed stories from 1936. It was re-serialized in Analog, in 1964. This review says it was "probably the last passably decent novel" that he wrote.
Oh, no, wait - that's a different book, "The Other Side of Nowhere." Entirely different from "The Other Side of HERE."
At the S-F Encyclopedia: "The high and only superficially simple competence of the stories remains as Leinster's memorial. " This is intended as praise.