>>63346
>I think the first half was stronger than the second
I concur. When they start to resolve the mystery and give answers and actually getting to the conclusion it gets flat. The same with Interstellar. And with Lost - the telly show - too, but that's a different category.
I think it's like this because the mystery itself, the contacting an alien civilization, the scientific, the moral, and religious mystery is given, we are living it. So building that up is easier than giving explanations that are as interesting.