To begin with, I thought the first season was pretty fucking great. I thought this one was even better.
The first season ended with Will (originally lost in the Upside Down) brought home and all things returned to normal...until a slimy something or other comes out of his mouth and crawls down his sink. Eleven has also been presumed dead after destroying the demigorgon...though there's the hint she's still alive and living out in the woods thanks to Chief Hopper's daily rations of waffles.
That's a pretty fucked up summary for someone who's never seen the show, but it'll suffice for the moment.
We return to Hawkins, IN, to find that the Shadow Monster (seen below) has become a more omnipresent force in Will's life. He keeps returning to the Upside Down in short, episodic bursts. These episodes are related to the new batch of doctors and employees at the lab, all of whom seem to be more...altruistic in nature this time around.
Couple that with the appearance of a new girl in town, the red-haired Maxine (Max for short; Madmax on all the video games in the town's arcade, beating all of Dustin's high scores). After some awkward pre-pubescent actions, the boys convince Max that she should hang out with them. She becomes one of the crew, essentially taking over Elle's spot from last season.
What we find out is that Eleven has been hidden away by Chief Hopper in an effort to keep her safe from other less altruistic authorities. We also watch as Dustin finds a small, strange alien-esque creature in his garbage. This creature, the size of a large slug, eats, grows, and molts several times. Much to the chagrin of the group, they realize it was a baby demigorgon that's growing quicker than expected, killing cats and woodland animals in order to feed.
Meanwhile, the Shadow Monster has been slowly taking over the entirety of Will's mind and body, using him as a kind of conduit to wreak havoc on the town as its parasitic vines creep and grow beneath the ground, creating a cavernous maze where more baby demigorgons have hatched and continue to grow.
I'll mostly stop there with the summation of the new season. I find that there's plenty about this season that's fun to stumble into. I will say that I totally had a theory about Bob that never came to fruition, though I feel it would've been a more interesting path for his character. C'est la vie.
What I enjoyed about this season is much the same about what I liked with the first season. I think there's plenty of really great imagination being put on display here. In the first season, you had Winona Ryder's character pretty much turn her home into a light up Ouija board in an effort to contact Will while he was stuck in the Upside Down. I thought this was a real stroke of brilliance, though it was super weird as fuck initially.
The parallel to this action in the second season is when the family tries to get Will to talk about what it is the Shadow Monster wants. When he can't vocalize it, he's given paper and crayons, creating what becomes a giant map of the area showing all the underground tunnels the Shadow Monster's demigorgons have created beneath the town. It's fucking insane and it's beautiful at the same time. I don't know who's idea that was, but it was great. The map in its entirety ends up covering nearly every inch of the house; the walls, the floors, the furniture, everything. Fantastic visual once they reveal it all.
The writing of the show had plenty of places where I thought they might drop the ball and I found myself pleasantly surprised they didn't every time. Sometimes the second season of an overwhelming hit of a first season can end up suffering from a sophomore jinx/slump (see: "True Detective") due to forced writing or just a bad story lacking serious thought. This season was not that.
The story made sense in context to the previous season (it all tied together), the characters all still felt very real and were all well acted, and I was (most importantly) completely entertained for the entirety of the series. Even more importantly, we get more of Eleven's back story, even seeing her leave Hawkins while Chief Hopper is...inconveniently indisposed. She travels to Chicago where she uncovers more of her past. Had this series been longer than 9 episodes, I would've loved to have seen more of this, but what's there is pretty damn good. Something of a fun ethical dilemma is put in Eleven's way and we get to watch her suss that situation out.
Having grown up in the 80's, there still a very realistic nod to the era without going so overboard that you think "Yeah, yeah...WE GET IT. You're in the 80's. Jeez." The music was, yet again, totally on point with the nearly ancient-sounding synthesizers, and the plot moved quickly without getting mired in nonsense or moving too quickly past important things the characters needed to deal with in order to defeat the Shadow Monster.
Anyway, if you liked the first season, you're gonna like the second season.
If you loved the first season, then the second season will probably blow you away as it answers a lot of the questions that were left hanging in the air from the first season.
And of course...there's a little left at the end that gives us hope for the possibility of a third season, which I can only imagine will be as good, if not better, than these previous two, which were great all on their own.