I tend to take notice of K-lytic reports, even though they’re focused exclusively on Amazon, for the trends and comparisons tend to hold true across most of the popular retail stores, even if the raw numbers differ.
There were some interesting observations in this latest report about the relative health of various categories.
You may or may not be surprised to learn that Fantasy far out-sells and out-ranks Science Fiction, in those two broad categories — and by a very wide margin.
Looking purely within Science Fiction, Hard Science Fiction has been trending downward in popularity for a good few years, and shows no signs of recovery (yet).
On the other hand, once you get past all the franchise tie-ins, such as Star Trek and Star Wars novels, the most popular sub-category in science fiction at the moment is Science Fiction Crime & Mystery. This category has been trending upwards steadily for two years and shows no sign of slowing down. Quite the opposite.
Science Fiction novels have a long tradition of including crimes or mysteries inside their futuristic settings. One of the earliest I remember is Isaac Asimov’s Caves of Steel, and I’m sure there are SF mysteries that pre-date even that one.
But it has only been in the last few years that SF Crime & Mystery became a category of its own.
You can find Amazon’s category here.
Kobo doesn’t have a dedicated category, but a simple search comes up with highly relevant results, that look a lot different compared to Amazon’s “Most Relevant” search results.
Google Play Books’ search results are not nearly as relevant as Kobo’s, and Apple Books are even worse, but between Amazon and Kobo, you can pick up a pretty good range of samples in this “new” category.
And I would be remiss if I didn’t mention my own SF crime & mystery series, Ptolemy Lane Tales. The first book of the series is The Body in the Zero Gee Brothel, and I’m currently working on book 5 in the series (which hasn’t a title, yet).