The Three-Body Problem Series by Cixin Liu (The Dark Forest,Death's End)

The Three-Body Problem series by Cixin Liu is a hard science fiction trilogy centered around humanity's first contact with an alien civilization, the Trisolarans, whose planet's unstable orbit threatens their existence. As the two civilizations interact, a conflict unfolds, exploring themes of science, technology, and the fate of humanity.

• The Three-Body Problem
  A physicist uncovers a secret alien communication that leads to Earth's first contact with the Trisolaran civilization, setting off a chain of events with far-reaching consequences.
• The Dark Forest
  Humanity prepares for an inevitable alien invasion, with a brilliant strategist using a theory of cosmic sociology to defend Earth from the Trisolarans.
• Death's End
  The final showdown between humanity and the Trisolarans unfolds, with existential threats and the ultimate fate of the universe at stake.