The Dark Forest

The sophons see everything except human thought. The UN picks four Wallfacers, who build defense plans without telling anyone. Trisolaran agents expose three of them. That leaves Luo Ji, an obscure sociologist and the only target of a Trisolaran assassination order. He tests the dark forest theory: anyone who reveals their location in the universe gets destroyed. Luo Ji goes into hibernation and wakes two centuries later, when a single probe, the droplet, wipes out Earth's fleet. Two surviving ships flee. Luo Ji then threatens to broadcast Trisolaris's position to the whole universe, and the invasion backs off. Earth gets a truce.

1. ChangeLuo Ji becomes Saul

   Book 2's protagonist is Luo Ji, a Chinese sociologist who used to be an astronomer. On the show, the role goes to Saul Durand, one of the Oxford Five, whom S1 deliberately keeps in the shadows until the final episode.

   source ↗
2. ChangeFour Wallfacers become three

   In the book, the UN picks four Wallfacers: a former US Secretary of Defense, a former president of Venezuela, an English neuroscientist and Luo Ji. At the end of S1, the show introduces three, with Saul among them.

   source ↗
3. ChangeZhang Beihai becomes Raj

   Chinese Navy commissar Zhang Beihai becomes Raj Varma, a Royal Navy commander and Jin's boyfriend.

   source ↗
4. ChangeOnly the beginning, for now

   The Wallfacer project, which gives S1's final episode its name, doesn't show up until about page 100 of the book. Almost all the rest of The Dark Forest has yet to reach the screen.

   source ↗