"The Time Traders" by Andre Norton (1958)
"'They have other things besides a-j's here. This place is strictly hush-hush. Even the a-j's do not set down too often for fear they will be tracked by radar. Where have you been, boy? Don't you know the Reds are circling around up here? These fellows watch for Red activity, and the Reds watch them. They play it under the table on both sides."
It may surprise you to learn that Andre Norton was really Alice Norton, a woman who saw a lot of sci fi/fantasy novels published in the 40s and 50s. She was well known in her lifetime, even if many readers mistakenly thought she was a man.
"The Time Traders" is set against a background of Cold War paranoia. A team of Americans and a team of Soviets travel back in time to prehistoric England, where they intrigue against one another. The Soviets, the Americans suspect, have uncovered some kind of "lost technology" from a vanished race, and the Americans are desperate to both discover this race and to reverse a "technology gap" between themselves and the Soviets.
All of the characters that inhabit this novel are stock characters, seen in countless other novels from the same time period. There is the rebel looking for a cause, the experienced older man who guides him, the gruff general, the saboteur, and other types familiar from countless other pulp novels. Norton handles these characters in a deft, workmanlike way, and I could not fault her pacing or sense of character development.
What I can fault, however, are the causality issues which permeate this book. Such issues are endemic to the time travel genre, but they are particularly obvious in "The Time Traders." It is these issues that place this novel firmly within the gadget-driven, predictable order of science fiction, and separate it from more fully realized works within the genre.
For one thing, the mechanism that allows the characters to travel backwards in time is never described in any detail. Neither are the limitations on time travel adequately addressed. Time travel is only a plot device in "The Time Traders," and this is a shame because one gets the feeling that Norton, had she been more adventurous, might have used this plot device for so much more.
It is also never explained why the characters can only travel into the past, and not into the future. Neither is it explained why the characters can only travel to one period in human history. It is also never explained how their travel into the past wouldn't create a host of paradoxes, with or without their questionable doctrine of non-interference.
I wonder, for example, why two nations would bother squaring off in the recesses of British history. Why not instead travel into yesterday? By simply knowing how the stock market went the day before, the Russians or the Americans could have caused one another incalculable amounts of damage, and in such a case "blending in" with the local populations would have presented no problem.
This also brings to mind the continual time constraints that characters seem to be under. If, for example, you have discovered the Russians hiding out in the prehistoric Baltic, why fight them the next day, when they know you're coming? Why not fight them three days before that, when they didn't even know you were there?
I could go on, but anyone who's expended any thought on the idea of time travel can come up with many more examples on their own. It is such examples that continually popped into my head as I read "The Time Traders," and it was such examples that ultimately ruined the book for me.
"The Time Traders" isn't terrible, but I wouldn't recommend it. As late 50s science fiction goes, it is exceedingly average.