I haven't watched the show, but I've seen some reaction videos. For an adaptation, it hits a lot of the same beats, but it does have a few differences.
Bill is still alive in the game. He and Frank had a falling out and you don't see Frank until you see he hang himself. It wasn't a terminal disease. He was bitten and didn't want to change.
The death of Henry and Sam were very much beat for beat. But Sam wasn't mute and the discussion of "what are you afraid of" was spoken out loud.
There've been other differences, but those are the big ones that are sticking out to me at the moment.