Henry Kuttner and C.L. Moore were a husband and wife writing team who specialized in science fiction, occasionally dabbling in fantasy or horror. Sometimes they wrote solo, but many of their works were collaborations using pseudonyms, the best known of which was Lewis Padgett. Their mainstay was the short story, with which over the course of the mid-twentieth century they were very successful at selling to science fiction magazines. The book Two-Handed Engine, named after one of the stories contained within, is a collection of their best short literature. I have been reading it off and on for the past few months...more "off" than "on", I'm sad to say...but I've just finished reading five more of its stories...bringing the total read so far to thirteen. Their titles are: The World is Mine, When the Bough Breaks, The Cure, The Code, and Line to Tomorrow. Although distinctly different tales, all five are distinguished by the subject of time travel and an examination into the nature of personal identity and consciousness...
The World is Mine, the most humorous of the lot, plays around with time travel's paradoxes and how people (and some rabbit-like Martians) get carried away with coveting power over others. In When the Bough Breaks, a superman/mutant sends agents back in time to his infancy in order to better train him for his future of destiny...probably not the best of ideas. The Cure involves a businessman who experiences moments when he feels he is in another place and time...and maybe is even a different person. The Code has two scientists experimenting with a rejuvenation drug on one of their fathers...the results bring on a comparison to the legend of Faust and Mephistopheles...meaning that if you're not already acquainted with that tale, then this story is probably going to be lost on you! The last of the bunch is Line to Tomorrow, where someone keeps getting a misdirected phone call...from the distant future...
I'm just guessing here, but it seems that stories about time travel and personal identity must have been very popular back in the 1940s, when these stories were first published. And if you were a writer back then, pounding away at the typewriter and struggling to come out with material that would sell...and provide you a reasonable living in the process...then you would most likely pay attention to magazine editors and publishers when they told you what worked (and what didn't). And the result, at least with Henry Kuttner and C.L. Moore, was a steady stream of popular short stories with some very similar themes...