The book is a journey, not just of following the snow geese as they migrate from Texas to the Arctic, but it's the author's journey too - from illness to well-being, from the childhood home to beautiful lands and then home again, from restlessness (his own Zugunruhe) to the sweet weariness of having completed a journey, from familiarity to marvellous strangeness and back to familiarity once more.
The author notices everything. You have a sense of him as almost silent, except for what he writes. He absorbs you with his descriptions of places and other people, delighting your soul with the accuracy of his observations.
It's a peaceful book, restorative, hopeful and uplifting. You give a sigh of satisfaction at the end of the book, glad for having experienced it.