Quoting the WSJ article:
Among his most famous books were: "Price Theory," 1962 (with Rose Friedman); "Capitalism and Freedom," 1962; "An Economist's Protest," 1972; "There Is No Such Thing As a Free Lunch," 1975; and "Free to Choose," 1979, co-authored with his wife. "Free to Choose" also was a series on the Public Broadcasting Service.
The producer of that series, Bob Chitester, told the University of Chicago that Mr. Friedman's "insatiable curiosity" made him a different kind of thinker. "He set forth ideas without regard to their popularity or acceptability. He has been equally tough on himself and others in his search for tools of analysis that consistently and accurately predict outcomes in both micro and macro economics. And he has never compromised the resulting analysis to please those in power. Such courage is essential to the survival of a free society," Mr. Chitester said.
I think that quote sums him up pretty well. As I've mentioned before, I think that Capitalism and Freedom or Free to Choose should be read by anyone interested in economics.