Yesterday's Kin is another entry in the Nebula novella category. This one was not online, but my library carried it.
I can't help comparing this one to her last novella nomination, After the Fall...since the look and heft of the book is about the same. But I liked this one quite a lot better.
Earth gets a visit from an alien race. Except they aren't alien, they are human, spun off from Earth early in mankind's history. This gives Kress the most straight-up shot at working with aliens that are really pretty much like us. She takes full advantage of it by presenting a culture that is very different, having evolved under different pressures, but recognizable.
The alien humans come to Earth with very advanced technology, including a "star drive". Also a warning. Panspermia is part of the speculation here, and the aliens warn of a cloud of "spores" carrying a virus. Earth will pass through it within a year, the aliens 25 years later. The aliens do not know how to prevent or cure it and would like our help.
Kress extrapolates on current politics, speculating that our current divide will continue and isolationism will rise up. Makes dealing with the aliens rather itchy. But they are taking the high road, working through the United Nations.
The fact that these aliens are indeed human plays well into the story. It's very coherent and well written, probably my favorite so far of the novellas, though there have been several good ones. It's a short read but very enjoyable. 4 stars from me, that good.