Walking, originally a lecture Thoreau delivered in 1851 and presented on subsequent occasions, eventually congealed into a readable essay. The essay was published posthumously in 1862.
The Thoreau Reader is a good online site with annotations to the works.
Thoreau can easily be put in the category "doesn't do well with others." I find him so dismissive of human society, the urban experience, politics, Europe, and so many other things I value that I am personally glad we're not bumping into one another on our long walks in the woods.
That said, Thoreau is an advocate for Nature, what we now call the Environment. I am also for Nature, enjoying diverse flora and fauna. An Inconvenient Truth scared me to death.
As part of my "method" tourism and to get some sense of Thoreau's universe, I have started taking aimless walks in the woods. I am not in any danger of slipping away too far from civilization, as I still obviously can upload posts to the world wide web. But my cell phone doesn't work here. That inconvenience would scare the daylights out of most New Yorkers.
I'd like to present some snippets here of Thoreau's Walking:
"It requires a direct dispensation from heaven to become a walker. You must be born into the family of the Walkers."
"I think that I cannot preserve my health and spirits unless I spend four hours a day at least — and it is commonly more than that — sauntering through the woods and over the hills and fields absolutely free from all worldly engagements. "
"When we walk we naturally go to the fields and woods; what would become of us if we walked only in a garden or a mall?"
"I can easily walk ten, fifteen, twenty, any number of miles, commencing at my own door, without going by any house, without crossing a road except where the fox and the mink do. ...Man and his affairs, church and state — and school, trade and commerce, and manufactures and agriculture, — even politics, the most alarming of them all — I am pleased to see how little space they occupy in the landscape."
"In one half hour I can walk off to some portion of the earth’s surface where a man does not stand from one year’s end to another and there consequently politics are not, for they are but as the cigar smoke of a man."