Oddly enough - I found myself in the extact same boat of putting this game down for months and months and then restarted it recently, with it in mind of finishing the game.
Overall I felt a little disappointed with the game. I think the biggest issue for me was the length of it. I was just left wanting a hell of a lot more then we actually got. I believe the main story doesn't even amount to 30% of the game's progress bar which is terrible in my opinion. I know the idea was suposed to be 'it's all in one night' but have that night as maybe an Act 1 and then lead into more mayhem perhaps running up till New Years in terms of the story.
The other issue I felt was that Joker is the most over used villian in the Arkham games - and sure, Troy Baker does a hell of a job with the role, but it just felt like every other villian only really got 5 minutes of fame, when they could really carry the story on their own shoulders instead of having to rely on old faithful Mr J. Don't get me wrong - I like him as a character, but we've seen an incredible amount of him over the three main games of the franchise. Going back to my 3 act story - have Joker as Act 1, and then maybe two more (Riddle is woefully under used in the franchise as the guy that just leaves stuff dotted around to be collected).