Spell of the Sensuous is next on my reading list.
Also recommended: Beyond Civilization. Before I read it, I was pessimistic about what my reading experience would be like. I thought I wouldn't get anything new out of it -- after all, I had already read most of Quinn's body of work and I thought it was getting pretty repetitive. But this one felt really refreshing to read. It's not perfect, but I do recommend it.
I also second Left Hand of Darkness.
If you live in Cascadia, try Jim Pojar's Plants of the Pacific Northwest Coast for an excellent, may I stress well-organized, source of information.