"Idainaru Yume" (Great Dream) by Edogawa Ranpo, a mystery set in war times. It might appear to be a science fiction at first, but it's actually a spy conspiracy story.
We only need to turn a few pages to find a scientist talk about breaking the sound barrier, and on the next page he talks about challenging the speed of light. Somewhere around in the middle there is a different mad scientist talking about create very large scale weapons, including a giant magnet to attach to submarines for the purpose of deflecting torpedoes. It's absurd to think any of these ideas would be practical, and that's part of why they are so fun to read, especially relative to the rest of the story.
The majority of this story is not about science, but about spies and intelligence. The real "great dream" that the title refers to is this ambitious spy conspiracy where the Americans spent decades into to planting the perfect spy in Japan. A trick of this scale does not occur in novels very often, and it was very impressive how Ranpo delivered it.
This story was not one of the more enjoyable readings due to its heavy nationalist and anti-American tone throughout, probably because it was originally published during World War II. Fortunately, this book came with two extra stories that are quite enjoyable: these are murder mysteries that are more consistent in tone with Ranpo's other writings, and the second story has the familiar detective Akechi Kogorou. It was a more positive way to end the book than a fleet of war planes flying over White House.
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