To know "what really happened," read the Records of the Three Kingdoms
Chen Shou’s Records is terse and sparing of words, many key episodes given in only a few. Pair it with Pei Songzhi’s notes — Pei cites a wealth of later-lost sources, often in a note longer than the main text, and many details "the novel didn’t write but that are even better" are hidden in the notes.
To know "how everyone remembers it," read the Romance of the Three Kingdoms
Luo Guanzhong’s novel shaped our main image of the Three Kingdoms today, of high literary value and immense popular reach — but read it reminding yourself that "a good read" is not the same as "the truth." Read with that clarity and you appreciate the author’s narrative craft all the more.
Reading the histories and the novel side by side works best
For the same event, first see how the Records records it, then how the Romance writes it; set side by side, you see clearly what is historical fact and what is literary shaping — a method this site demonstrates in the "version differences" notes on a few figure cards.