It's as accurate as you could hope a musical to be, in my opinion. There's a fair bit of simplification and in some cases, assigning real historical actions to different historical characters. e.g., Lin has Jefferson, Madison, and Burr confronting Hamilton about the Reynolds money. In reality it was Monroe and some other senators... but ones who weren't already principal characters in the musical. Angelica was already married when she met Hamilton, but their letters to each other and contemporary accounts have them being quite flirtatious. Stuff like that.

If there is a particular aspect of the show you're curious about, that's easier to address than a catch-all question about a multi-hour musical :)