Thoreau's desire to meet and become well-acquainted with a Native American was fulfilled when he hired Joseph Polis as a guide for an 1857 trip in Maine. He was mainly impressed by Polis's ability to travel effortlessly in the wilds, and he subsequently wrote a portrait of him. That year also included the beginning of an economic depression, referred to as the Panic of 1857, which lasted for several years, and the Dred Scott ruling by the Supreme Court, which denied citizenship to all blacks. Thoreau also met John Brown and later became highly politicized at the time of Brown's execution following Brown's raid on Harper's Ferry, which was then part of Virginia. In 1859, Thoreau's father died, and he became the head of the family. The same year, Thoreau was appointed to the Harvard Committee for Examination in Natural History, which was led by Asa Gray, a prominent botanist; this was perhaps Thoreau's only scientific position; they conducted examinations of Harvard botany students.
Because of Asa Gray's friendship with Charles Darwin, he received an early copy of On the Origin of Species in 1860. He shared it with his friends, and Thoreau became one of the first Americans to read it. They had animated discussions about it at Harvard, and, of course, Louis Agassiz completely rejected it, because he thought that "all natural species were separately created by God, unchanged through eternity." That year, Thoreau also delivered a lecture titled "The Succession of Forest Trees." This was published in newspapers by Horace Greeley and became the most popular publication by Thoreau in his lifetime. In May, 1861, Thoreau went on a trip to Minnesota and returned via Canada. In Minnesota he met Native Americans. After he arrived back in Concord in July, his tuberculosis worsened, and he died on May 6, 1862 at the age of forty-four.
My lack of enthusiasm for this book continued right up to the end. One aspect of this, as I mentioned, is Walls's writing style. Although she has the appropriate academic credentials, she projects a Thoreau-fan-club aura that tends to result in an absence of critical appraisal. That can work to a certain extent, because Thoreau doesn't really fit the model of a major thinker, and, describing him the way that she does, it becomes clear that he was informed by the environment in which he lived, which can alternatively be seen as the subject of the book. So, even if Thoreau wasn't that great, you get a highly detailed picture of the culture in Concord during the mid-1800's. Unfortunately, I'm not a cultural historian.
As for Thoreau himself, I don't currently find him particularly interesting. That is because I am not impressed by his ideas. I think that is partly his fault, because he spread himself too thin. He delved haphazardly into so many subjects that failure was almost guaranteed. His interest in Native Americans could theoretically have been developed into an early anthropological study, but it wasn't. His interest in the regional effects of farming on local ecosystems could have been developed into land management science, but it wasn't. I also think that his political writings tend to be naïve and uninformed. Then, although he delved into Buddhism and Hinduism, he did not seem to make a real departure from New England Puritanism, because Transcendentalism seems merely to be a variant of that. I think that Thoreau's scattershot way of choosing subjects was the result of his family background and the time and place in which he lived. He had no model in his household for choosing a career and pursuing it with a college education. Furthermore, Harvard at the time was nothing like a modern research university and was similar to Oxford and Cambridge, which were also still functioning like theological seminaries. Charles Darwin himself could easily have ended up as a clergyman, because he did not distinguish himself academically at Cambridge. So, although Thoreau seems to have been talented, he lacked a career plan and ended up spreading himself too thin. As a writer, he didn't have a practical strategy for developing a wide readership. In other respects, he held many of the prejudices of his time; for example, he thought that women were stupid: technically, he was a sexist. Then, as a writer, I don't particularly like his style, which seems archaic to me. Overall, I think that Thoreau fits best within the context of later developments such as the civil disobedience protest strategy and the interest in nature-friendly lifestyles, but I don't think that he provided any definitive writings on those or other subjects. It is possible that, had he remained in good health for another twenty years, he may have produced something more closely resembling a magnum opus than Walden.