Mercy of the Gods is James S.A. Corey’s follow-up to The Expanse and the first book in the planned trilogy called The Captive’s War. Since Corey’s The Expanse is my favorite sci-fi book series, I think I was primed to enjoy Mercy of the Gods. And, guess what – I did enjoy Mercy of the Gods. A lot. 
That being said, Mercy isn’t just more of the same. The Expanse jumped genres quite a bit – some books in the series were Westerns, some were mysteries, and some were action. To me, Mercy is more like hard science fiction. Corey focuses a lot more on biology and its relationship with anthropology. The focus on biology brings biologists themselves to the forefront of the story. In particular, a team of research biologists is plucked from their lab and the petty squabbles of academia and dropped straight into the middle of AN ACTUAL ALIEN INVASION.
Corey is so good at using the internal experiences of a few point-of-view characters to explore larger events. I think the book is at its best when the point-of-view characters are trying to understand an invasion in real-time. What do you do? Drink with your friends? Hook up? Watch the news? Garden? Find your freeze-dried food and hunker down? How quickly can you adapt? Or should you adapt? How do you honor those left behind?
I also enjoyed how opaque the alien culture and technology appear to humanity. To a certain extent, we understand why and how humans do things individually and collectively. But how can you negotiate with alien invaders when you don’t have at least some shared reference points or axioms? Trial and error could be fatal, locally and globally.
This was one of my favorite reads of the year, easily.