Russian Doll is billed in some places as a comedy, but it's better than that. Ok, maybe that's a bit unfair. Comedies can be great, and profound. But Russian Doll is something else.
Its basic template is Groundhog Day: Nadia is caught up in a recurring loop which obliges her to live part of a day or longer over and over, until, as she comes to learn, she corrects something in her past. The spice is that the trigger of each loop is death—hers. The breakthrough into new and rich narrative is she discovers, about half-way through the eight 30-minute episodes, that she's not the only one who's dying into recursive loops—so is Alan, whom she meets in an elevator, on its way to crashing and killing its passengers, but Alan, like her, knows what's coming.
This sets in motion a folie à deux between the two, actually a reality, as Nadia and Alan begin to realize the hard way that by working together they can stop their recurring deaths, by coming to terms with the destructive issues in their lives which somehow started all of this in the first place. For Nadia, it's the guilt she feels about her mother's death after Nadia as a child left her. For Alan, it's understanding why his girlfriend of nine years left him. But those specifics hardly matter. It's the way these two work things out, and the impact that has on those around them, that is the meat of this narrative.
And, indeed, the one reservation I have about calling Russian Doll a complete success is that I liked that process, beginning with the introduction of Alan, better than the resolution. Without giving everything away, that ending entails reality itself splitting in two (calling Counterpart), with a knowledgeable Nadia and an unknowing Alan in one, and a knowledgeable Alan and an unknowing Nadia in the other. This facilitates each one educating the other. Well, I guess that does give a lot away, but at least I haven't told you how it all turns out.
But pulling that ending out of some metaphysician's hat weakens, I think, an otherwise brilliant and original composition on time loops. Still worth watching, and eminently recommended, with fine acting by Natasha Lyonne as Nadia (one of the creators, along with Leslye Headland and the Amy Poehler) and Charlie Barnett (Chicago Fire) as Alan, and great New York locales.