I just learned the sad news of Derek Bailey's passing this past Christmas Day in London. There's a nice write-up here. There's also a streaming 3-hour tribute here.
His book on improvisation is one that I've read about three times and I'm due to revisit it again. It is an honest and well thought out account and virtually the only prose that does the subject justice. His music is equally amazing. The man had big ears and a great mind. It is fiendishly hard to write about improvisation theory. He succeeded by balancing between intellectual rigor and passionately introspective reflection. The same could be said of his playing.
Derek Bailey: 1.29.1930 - 12.25.2005