Fair warning: you should not read this book if you are having a "boo hoo, I'm going to die alone in a box under an overpass" moment. But otherwise you should definitely find a copy and read it. It's short.
I've only read three of Barbara Pym's books but I have a blog and no one can stop me from saying that Quartet in Autumn feels supremely Pymmian. The four main characters are all odd and unattractive; elderly people working admittedly useless and unskilled jobs, with very little apparently in their lives. The four don't really seem to have or want much of a relationship beyond their occupation of the same office, and when the two women retire not only is it uncertain what they will do with their time it is also unclear whether there is any relationship beyond the work relationship that can continue.
One of the threads in the book involves a well-meaning but frustrated social worker who finds visiting one of the retired women very unrewarding indeed. Lonely old dears might be cranky at first but they're truly grateful for the attention... eventually... right? The humor in Quartet in Autumn is less pronounced than in Excellent Women or Glass of Blessings but it's here, mostly making the point that sometimes a crusty exterior serves to hide an equally crusty interior.
There are a couple of other characteristically-Pym elements to this book. First, I think I commented in another Pym review that she portrays how badly plotted life can be, and here, instead of characters being pushed together by circumstances or discovering their feelings for one another, opportunities get hinted at and missed, and people are not particularly sorry for having stuck to the knowns. Secondly, the whole thing ends on a genuine, organic note of hope despite there not being much concrete foundation for it. I'm not an author (clearly) but I can see where it's easy to create a hopeful ending by, say, giving your character some cash or tickets to Paris or a new romantic interest. Pym gives her characters very little -- arguably in this book she takes away some of what the characters had in the beginning -- and yet she ends with new hope by allowing the characters a change in perspective. Or I wonder if it would be more accurate to say that the characters derive hope from a rediscovery of their own ability to choose. I'm thinking of this little Christian/Catholic book recommended by a friend, Interior Freedom, which discusses the idea that even if one is dissatisfied or unhappy with a situation, one can be at peace with it by freely choosing to endure it (obviously that's not a novel idea but this is the book I thought of off the bat). I wonder if that would be a better characterization of the way Pym's characters end up with a sense of a new beginning or if I'm refining it too much; it might fit with the Anglo-Catholic theme that runs through her books.
Quartet in Autumn is about old people and is mostly about how their problems are not easy to solve. It's not a sexy exciting book about sexy exciting people by any means. But they're not kidding on the back cover when they call it a masterpiece, and you'll be glad you read it. You'll also want to go open a retirement account, cultivate your relationships with your nieces and nephews, and otherwise figure out what you want life to be like when you're old.