Which is why we're doing this now instead of in December.
Excluding flashbacks and an epilogue (which does take place at Christmas), the series takes place over a few days in what's presumably late November. Christmas decorations have started going up, but they're certainly not ubiquitous, and stores are stocking holiday lights.
It's those lights, incidentally, that I mostly want to address. The story of the series centers around --
Oh, yeah. Spoiler Alert, and all that.
Where was I?
Right. The story centers around a missing child who's pulled into a parallel universe by some sort of alien monstrosity. I say "parallel universe" in keeping with the series, but in current geek parlance, the term "alternate dimension" might be closer. Alternate universe isn't technically inaccurate for this sort of extra-spatial anomaly, but going with dimension helps to clarify that it's less a separate reality than a hidden one. I trust if their nerdy science teacher had a better understanding of the situation, he'd have gone with that turn of phrase instead of bringing up Everett's Many Worlds Interpretation.
The significance of this focuses on the way people and creatures in this parallel dimension (dubbed the "Upside Down" in the show) interact with that of our own. It creates electrical and magnetic interference, which plays haywire with lights. This is where the aforementioned Christmas lights come in: when the missing boy's mother concludes her son's alive, she purchases and hangs tons of Christmas lights, first to track his movements, then - with a hastily painted alphabet - to communicate.
It's both a beautiful image and a novel integration of holiday tropes in genre, and I thought it justified mention.
As I mentioned earlier, the epilogue is explicitly set at Christmas, complete with holiday sweaters, presents, and snow. It's meant to both wrap up character arcs and set up a few unanswered questions. The sheriff leaves food scrounged from a holiday party in a box in the woods, implying El might still be alive. Nancy gives Jon a camera to replace the one Steve broke. And, in classic Christmas tradition, Will vomits up an alien slug into the bathroom sink. You know, in case they want to make a second season.
The closing does a decent job playing up the strange feeling of the holiday season, implying a renewal of mystery and magic - both good and bad. In this context, the epilogue could be viewed as a variation on the solstice.
Or maybe they just wanted to toss in an allusion to Gremlins, since they'd basically hit every other genre movie from the 80's. Who the hell knows?
I don't have too much to say about the rest of the series that hasn't been covered elsewhere. I like the series quite a bit, though everything came off as a little too generic. It felt like they were so interested in nostalgia, they created an 80's genre smoothie. That's not a bad thing - like I said, I liked it quite a bit - but there was nothing that felt unique to this story or these characters. Because of this, there wasn't really much to love.
Still, it's definitely worth checking out if you're a fan of pretty much anything made in the 1980's.