We don't have an HBO subscription so I was able to view this limited series (7 episodes, each roughly one hour) on a set of DVDs from my public library. My wife started with me but abandoned it after just half of the first episode, she didn't like the brusque nature of Mare, but that is part of her character arc, influenced by losses she had recently suffered. I believe my wife would have enjoyed the series if she had stuck with it.
It is set in the somewhat fictional town of Easttown, but in fact much of it does take place in the real Easttown Township, Pa. A community where most everyone knows everyone else and many are related to each other. A community where people often don't even knock or ring the doorbell when going to visit someone, they just walk it.
There are two significant crimes causing community friction, one is the disappearance of two young ladies, the other is a murder of a third young lady. They might be connected, they might not. Much of the roughly 7 hours of running time is in some way associated with trying to solve those crimes. They eventually are, they involve people of the community, and there are some big surprises along the way. And there are a number of Red herrings to keep the viewers guessing.
It is clearly fiction but what makes it so good and so interesting are the characters that really could be real people in any small community. Plus the dialog is uniformly well written. The discs have a number of interesting "making of" extras and it is revealed that Winslet often modified the written dialog, adding or substituting things that would make Mare more realistic.
Watching the whole thing is a big investment of time but I am glad I did, overall very interesting. And Winslet shows why she is one of the best of her generation.