Death's End (The Three-Body Problem Series, 3)

Cixin Liu's Remembrance of Earth's Past series seemed to end nicely with Dark Forest. Alas, with Death's End, we see that the "end" was not really an end. This book goes way beyond the worries of our mere instance on earth to explore questions of the universe over time periods of millions of years. 

The book primarily focuses on the experiences of a few key figures. They often enter hibernation only to awake in a time that is very different than what they recall. The shifting mores of society can make the heroes of one time period become the villains of another. The earth is in an uneasy truce with TriSolarans. There is a single person that has the ability to trigger the "message" that can lead to the destruction of the solar system if the "invaders" try too much. The two species have gradually become closer, adopting parts of each other's culture and technology. Meanwhile, humans have become effeminate and light on defense. They seek to bring back the few ships that are at the outer reaches of the galaxy to try them for crimes against humanity. There are also attempts to limit technology due to fears. Alas, it is only through some of these that "slip through the cracks" that humanity is able to continue to exist.

The earthlings finally try to swap out the "man on the button" with somebody new. Alas, she is not as callus as the man that had been their previously and the Trisolarans take the opportunity to wipe at the signal transmission technology. The Trisolarans then show their "compassion" by given humanity one year to transfer everybody to Australia. Seems an obvious parallel to the "reservations" that conquerors have consigned native populations to. These humans must live a  primitive life with no technology. Due to severe overcrowding, they are also expected to fight each other to the death in order to survive. A few select people are part of a military force that rounds up stragglers on the other parts of the earth. 

Things look bleak for humanity. Luckily one of the ships that was flying away happened to be outside the realm of the Trisolarans communication mechanisms. They see they are about to be overtaken and send out the message, telling the world about the TriSolaran home world (and identify earth.) The TriSolarans immediately give up their hopes of earth. Humanity is given a reprieve. The people that had been "lucky" enough to be on the police force are now tried for crimes against humanity. (This seems to be a recurring theme.)

Now humanity is in a race to build technology to survive after an impending attack. Luckily they get a communication from a human that is embedded with the Trisolarans. He tells a story with hints of requisite plans told a few levels deep in a story. They attempt to decipher it and use it to work on some technology development. However, concepts of slowing light speed or building light-speed travel are shunned in favor of bunkering people near Jupiter. Alas, the attack comes via a different means than expected and light speed travel is the only solution. Luckily, some technology was created (even after it was prohibited.) A few humans escape.

Things jump forward millions of years. We learn that some  people are hidden behind a "Slow light" world that makes them safe, but eliminates outside contact. Beings have been fighting using the laws of physics that ultimately will lead to the destruction of the universe. The dimension-shrinking weapons are used to eliminate threats. Alas, these will eventually shrink the entire universe to smaller dimensions, leading to the destruction of the entire universe. This end seems to be rushed, as it quickly changes the scale of problems.

The underlying assumption is that the universe is a cruel place. Species would rather inhiliate others than attempt to peacefully interact. Humans are also prone to focus on the moment. Long term planning is difficult and politics often force dumb decisions to be made. People are also very prone to judge people of the past, applying standards of today to very different situations in the past. Identity frequently shifts based on needs. When at peace, people splinter off to individual subgroups. When there is a big conflict, people unify. (Though for some reason, hibernating people are still supported through these great upheavals.) Human existence is ephemeral. It is hardly a blip on universal or geological time. Should we be concerned of out lasting legacy?