The Three-Body Problem is a science fiction novel written by Liu Cixin. It is the first book in a trilogy that explores humanity's first contact with an alien civilization. The story follows a group of scientists who uncover a conspiracy involving the Trisolarans, an alien race from the Alpha Centauri system. As they try to decipher the alien's intentions and prepare for an impending invasion, the characters grapple with the implications of their discoveries and the limits of human knowledge. The Three-Body Problem combines hard science fiction with philosophical and sociological themes.