Adam Troy-Castro has combined elements of scifi with the "locked room" mystery to great effect in his Andrea Cort Novels. I know
Emissaries from the Dead and
The Third Claw of God are both available in ebook form (in the US anyway).
There is an uber-plot to the the whole series, but each book can be considered a stand-alone whodunnit. It may not be exactly what you're looking for, but I thought I'd throw them out there.
