It's really slow
I'm watching it now and I'm trying to like it. The man lived a very interesting life.
There are three problems:
Pacing: It is highly focused on 1981 and the rest is flashbacks, but the flashbacks aren't really that interesting and way too sporadic.
Too much focus on the writer, Stone. I don't care about his personal life, his dating that woman down the hall, his ex-wife, and his financial issues.
It's rather dull. There isn't a lot of passion or drama here. I don't feel connected to the characters enough. There is really zero suspense.
Harvey is great and gives an understated performance. Worthington actually does a decent enough job though I wonder if he was miscast.
In summary, it's an average movie about an incredible story.