(If you've never read any of Sontag's critical writings, Ed Champion provides some good links to essays, interviews, and miscellanea.)
I've read Against Interpretations and Other Essays numerous times and have kept a copy nearby since the early years of college. First, it taught me that there was a lot I didn't know about the worlds of literature and film, and, indeed, the world itself. Then it provided me with ways of thinking about aesthetic experiences. Ever since, it has offered familiar words along with something different to argue with and against each time. I've never felt compelled to agree with Sontag, but I've always felt compelled to read her, to reread her, to think about what she has to say. There are other writers of essays and criticism that I enjoy more, certainly many whose tastes are closer to mine, but none whose work has so frequently caused me to re-evaluate not only what I value, but how.
One of the things that I have most enjoyed about Sontag's work is her ability to cross between various art forms, historical periods, and ideas. I've spent most of my life bouncing between the realms of literature and theatre while also maintaining a (very) amateur interest in film, and thoroughly dilettantish flirtations with such subjects as art history, philosophy, and music. Sontag always seemed to know more about those subjects than I did, and she knew things in such interesting and provocative ways that I always wanted to find out more.
Sontag's willingness to write in various modes -- to write fiction and plays, to create movies -- while all the time continuing to write various forms of criticism, seems to me another model worth emulating. One of the problems with the theatre world is that too many practitioners are not critics and too many critics are not practitioners. I don't think a critic needs to be a particularly good creator (Sontag's success as a fiction writer and playwright was mixed), but they can speak with more authority when they have at least attempted to live through the process of creating something other than criticism.
In the "Note to the Paperback Edition" of Against Interpretation that I have (a sun-stained and life-scarred old paperback with a remarkably strong binding), Sontag writes:
Before I wrote the essays I did not believe many of the ideas espoused in them; when I wrote them, I believed what I wrote; subsequently, I have come to disbelieve some of these same ideas again -- but from a new perspective, one that incorporates and is nourished by what is true in the argument of the essays. Writing criticism has proved to be an act of intellectual disburdenment as much as of intellectual self-expression. I have the impression not so much of having, for myself, resolved a certain number of alluring and troubling problems as of having used them up. But no doubt this is illusory. The problems remain, more remains to be said about them by other curious and reflective people, and perhaps this collection of some recent thinking about the arts will have a certain relevance to that.A perfect credo for a critic, it seems to me; a perfect process of thinking. The "problems" Sontag spoke to do, indeed, remain, and always will, because they are the deep puzzles and wonders of art: what do we value and why? how do we talk about what we value? how do we learn to value more than what we do without sacrificing integrity? Etc.
The problems remain, and I hope they always will, but we have lost one of the best thinkers to have tackled those problems during our lifetimes.
Update 12/29: The NY Times has opened up the archive, and there are some wonders in amidst the blather. A couple days ago, if asked to name three favorite critics (living, American) I would have said Sontag, John Leonard, and William Gass. Here's Leonard on Sontag's Regarding the Pain of Others:
So much, then, for Guy Debord, Jean Baudrillard and their French-fried American fellows in the media studies programs, looking down on staged events as if from zeppelins, or like the kings of Burma on the backs of elephants, remote and twitchy among the pixels, with multiple views in slo-mo, intimate focus or broad scan, and an IV-feed of chitchat. When we think about the pictures we have seen from Bosnia, Rwanda and Chechnya, about the videotapes available to us of Rodney King being beaten and Daniel Pearl being murdered, media theory seems merely impudent.And here's Gass on the book Regarding the Pain of Others was meant to amend, On Photography:
One realizes, reading Susan Sontag's book, that the image has done more than smother or mask or multiply its object. My face is only photography, and people inspect me to see if I resemble it. The family album demonstrates to me what I don't yet feel: not that I was young once, but that I'm old now. Time, so long as it lingers in the look, is visible to us in this photographic age in a way it was never visible before, among familiar things, we fail to measure change with any accuracy; but the camera records one step upon the stone, and then another, until the foot has worn a hollow like a hand cupped to catch rain. Process has become perceptible in the still.Now, if only I knew whether Guy Davenport or John Clute had written about her, the circles of influence would be nearly complete...