Boy, this one's a La La Land-like heartbreaker!
Story-wise, it's a very, very slow burn. The first hour feels totally wasted...until...and then KERPOW!!! After which, it hits you like a brick and leaves you weeping in your seat.
Now, it's resting at 6.3 on IMDB, and I do think that's because Acts 1 and 2 lack some sizzle, but if you can survive them, well, you'll be rather positively impacted by Act 3.
Just hang in there. On balance, I think it's worth the wait...