The final scenes of the novel act as the opposite of an epilogue. Usually, an epilogue wraps things up nicely and gives us a rundown of all the characters. There are a ton of examples, and, well, this isn't one of them.
In The Heart Is a Lonely Hunter, the ending gives us glimpses into the beginnings of brand new stories and hints at futures that we'll never get to know. As a result, the ending is really open for interpretation. We feel hope and despair for each of our main characters, and the whole experience is pretty unsettling. Which is fitting, really: the entire novel is structured around a series of emotional, often unsettling vignettes – snapshots of the main characters' lives.
The end on this novel is made up of four interconnected vignettes that take place over the course of one day. In this way, the ending mirrors the first few chapters of the novel, which also take place over the course of roughly a day. We get short glimpses into the changes and turning points in the lives of our main quartet: Doctor Copeland, Jake Blount, Mick Kelly, and Biff Brannon. Things look bleak for all four, who are struggling in the wake of their shared confidante's abrupt suicide. In a way, Singer's suicide is really the end of the story and the concluding episodes are just teasers into new beginnings.
One last thing: the very, very end – that is, Biff's ending – is actually kind of hopeful. What do we make of that in a book that's otherwise pretty bleak?