1. A Walk in the Woods - I was going to suggest this as well. Similar to what Cahill's writing did for me, I loved the descriptions of both history and the environment that pull me in and are more relatable to my sense of what adventure means. However, I won't harp on this one because I know that other people have put in similar good words.
2. The Things They Carried- I know everyone reading this blog post has read this already because it was our freshman year reading but I think it would be a good option for classes who have not read it for orientation. This book bring in new angles of adventure- there is travel, packing, gear, but also violence, loneliness, politics. It is a fantastic read and I think could expand upon the adventures people embark on. By choice or not by choice- how we deal with them- what they bring into our lives or take away from it etc. While it departs from the horizontal & vertical themes I think it could be interwoven well into the class. I also think there are interesting parallels between the uglies of war and what it does to humans and the immeasurable dominance of nature and what it does to humans- the mentalities required as well as the psychological journeys that can occur.
I've so enjoyed this class with all of you! I hope you all have the adventures you dream of!