I don't often have these reactions, but here it is: the season was very good, the last episode superb - and it's quite possibly the last time I watch the series.
The out-of-character killing of James by Nucky was simply nauseating. It (together with the Margaret marriage sham) made him seem like a totally monstrous, unscrupulous character - and unless I'm led to believe he is for a longer period of time, like in case of Tony Soprano or Thomas Kane (Boss), it just seems odd, unnecessary and simply - wrong.
It is also not in the vein of Sean Bean getting the sword in Game of Thrones; no, there it followed the narrative of the evil and corrupted. Here, the narrative pointed to redemption, not the evil in men. The death of James followed nothing, signified nothing - it was just thrown in there like a pathetic explosion of bad taste.
I have no desire to follow the character of Nucky Thompson now - he holds no value - and in my opinion this screwed the entire series up. I'll take a look at the episode in which he gets killed, not before, I think. A great, great shame.