I suppose I should add this to currently reading, but it's something I just pick up every few months and read 20 pages or so.
I've found this of great interest because John Muir is something of a personal hero of mine. He did more than anyone else to help preserve the American wilderness (with some notable failures, like Hetch Hetchy), and wrote about it beautifully. This collection of mostly letters gives insight into the times, his personal relationships, and how his thoughts on conservation developed over the years; it also contains several of his non-seminal writings.
He led an interesting, enraptured life and is someone I'd love to (hypothetically) meet; I've long admired his intelligence and passion for nature, that were coupled to a rare pragmatism. I've had this book for several years, even before unintentionally moving one mile from Muir's long-time in Martinez. The home and what remains of the orchards is still beautiful, but I don't think Mr. Muir would be overjoyed about the six-lane freeway running a few hundred feet from his home (and, ironically, named after him).