By Clifford Geertz
Confession: I am really not a fan of Geertz. I recognize that I only have that luxury because his work was groundbreaking enough that it can seem obvious in retrospect. But I would still rather read derivative work, which tends to show more economy of writing that Geertz's.
Now that we have that out of the way, let's focus on the most often cited essay in this book: "Thick description: Toward an interpretive theory of culture." Here, Geertz discusses the notion of thick description, borrowed from Ryle (p.6) and elaborated. Geertz distinguishes between thin description (what is someone doing?) and thick description (what does that action mean in terms of cultural categories?) (p.7). The example here is that of a man rapidly contracting his eyelid (thin description) as a burlesque wink (thin description). Thick description, Geertz argues, distinguishes good ethnography from bad (p.16).
That's a very (ahem) thin description of the essay, but it's the gist of what—I concede—you probably should read for yourself. Although I find Geertz's prose to be a chore, he does provide a thorough, example-laden argument for understanding description as an interpretive move that ethnographers have to embrace and practice. If you're interested in doing field research, ethnography or not, this essay should help you to understand and sift through some of the layers of meaning you'll need to describe. For that reason, yes, read Geertz.