"'In the beginning I was so young and such a stranger to myself I hardly existed. I had to go out into the world and see it and hear it and react to it, before I knew at all who I was, what I was, what I wanted to be.' So begins Upstream, a collection of essays in which poet Mary Oliver reflects on her willingness, as a young child and as an adult, to lose herself within the beauty and mysteries of both the natural world and the world of literature....