Those who've been energized by our recent discussion about art, and who don't know Robert Adams's little book Beauty in Photography: Essays in Defense of Traditional Values, may want to take this opportunity to pick it up. It's a brief collection of beautifully-written little essays (sorry for repeating the adjective, but it's the only one that will do) by a prominent working art photographer. The book originally came out in 1981 and has already stood the test of time. It's very inexpensive to buy ($10.17 at the link) and easy to savor all at once or one essay at a time. Who knows how long this newest edition (which came out in 2005) will stay in print?
The essay that stands out most prominently for me over the years has been "Civilizing Criticism," but none of them will waste your time. Warmly recommended.
ADDENDUM: ...And here's a link to Why People Photograph, the other half of the author's matched set.