Martin Buber's I and Thou has been in print since 1923 and is still one of the hardest short books in modern philosophy to actually use. Its argument is that there are two fundamentally different ways of standing towards the world, and only one of them makes us human. Its prose is aphoristic and compressed, and most readers finish it with the feeling that something important has been said and no clear account of what.
Saying You lays out Buber's thought in order and in plain language, drawing on the later essays where he sets out the same ideas far more clearly than he ever did in I and Thou.
You will come away understanding:
Buber is worth reading because he offers a genuine alternative to the picture of the person that runs from Descartes onwards - one that starts from meeting rather than from a mind alone in a room. He worked it out independently of the existentialist and phenomenological traditions he is usually filed alongside, and he spent fifty years testing it against religion, art, psychology and politics rather than leaving it as an insight.