I read this graphic novel compilation a few years ago, but in the interest of giving myself a more thorough education regarding the villain of Avengers Infinity War, I decided to read it again.
This story was a segment in a much larger story arc involving the Guardians of the Galaxy, the Nova Corps, the Inhumans, the Shi’ar, and several other galactic entities. The thrust of the plot is that several events have had the combined effect of ripping a hole in the division between “our” universe and another one were death has been defeated, so nothing there ever dies. As a result, that 2nd universe is over-populated – they plan on taking over our universe to give them more room to expand. Thanos is the key to re-introducing death to that 2nd universe and preventing them from overtaking ours.
I gave The Thanos Imperative four stars as a stand-alone read. There is a lot going on in this story, and it’s easier to follow if you also read some of the volumes leading up it.