Death's End, by Liu Cixin and translated by Ken Liu, is the third and final installment of the Remembrance of Earth's Past series. It chronicles the events following The Dark Forest and focuses on humanity's place in the universe. There is a lot of interesting science/science fiction concepts presented in this hard sci-fi novel, which keep you thinking on it for days on end.
Read on for my review, but bear in mind that as the third in the series there may be spoilers for The Three-Body Problem and The Dark Forest.