Look, listen. Nagato was best girl in the Haruhi series. Would be nice to see more of her, yes? Oh, look! An anime about Nagato. Well, you might think so, if you read the title but you are wrong, very wrong. The voice actress is the same, the character design is .. roughly the same? The artstyle is definitely different and I guess it's a question of personal taste but Kyon looks almost nothing like himself. Nagato's personality is not the same. It's like they took everything that made her great and threw it right out the window. What you're left with is an incredibly boring slice-of-nothing anime with characters that could be easily replaced with cardboard cut-outs. Remember Koizumi? His one single role in this anime is to simp for Haruhi and simp he does.
At the very least there is a little bit of fanservice - mainly done by showing off Nagato's PSVita, what a gem. (
The next section will contain spoilers, but honestly just read it, spare yourself from watching this:
For some stupid reason both Nagato and Haruhi fall in love with Kyon after like one interaction with him. In Nagato's case he helped her get a library card, in Haruhi's case.. he said that maybe Aliens do exist, or something. BAM - love. You might think, well, maybe this rivalry will become a major plotpoint in the series? It doesn't. It goes nowhere, just like the rest of the anime.
The best part of the anime are 3 episodes in which Nagato's personality changes due to a 'traumatic' car accident. She basically becomes 'Old Nagato' but all too soon the tumor that is New Nagato's personality starts to spread. Of course, this Nagato also falls in love with Kyon and she actually manages to confess her feelings before she 'dramatically' disappears, letting New Nagato take control once again.
It only goes downhill from there.
Kyon acts awkward around Nagato after 'her' confession, there's a whole lot of nothing + some nods and referenced to the Haruhi series - you know, an actually good anime?
And don't get me started on the last episode.
They go to a summer festival, including a firework show. The PERFECT opportunity for Kyon to confess, that he too has fallen in love with Nagato, amirite? As the trope goes, he tells her everything but - oh snap - Nagato couldn't hear a thing! No kiss, no clarification but for some reason Kyon feels like he accomplished what he had set out to do, pats himself on the back, and moves on. It's like nothing ever happened since Episode 1.
Oh yeah, and of course the end teases us with a reminder of the endless eight, setting up for a timeloop-scenario that will be covered in the OVA.

Should you watch this anime? No. No, don't. Even if you liked Nagato? Yeah, run, don't look back. Do not let your memory of Nagato be ruined by this generic, trope-abusing, boring piece of media.