This is a sad, lonely film full of stillness and melancholy. David Lowery's movie is full of long, uninterrupted sequences of the mundane. This movie seems very focused on a very specific story but each segment drips with symbolism on humanity, companionship, and religion (or at least the concept of God.)
The acting is well done, but 80% of the movie is watching Casey Affleck in a sheet with two eyes cut out, playing a voyeur to whomever lives at the property he lived in. That voyeur aspect is what will make or break the film for you. Will you be willing see beyond the surface, or will you be too frustrated by 4 minutes of Rooney Mara eating pie?