Very sad, and the circumstances were additionally sad.
He was diagnosed about a year ago, and given between 2-4 years to live, was receiving various treatments and by measurable standards the disease appeared to be in control. Around 2 weeks ago there was a rumor that he was actually on his deathbed, a post was made to his blog on the 9th(by his cousin i think) saying that the rumor was completely false and while he obviously was not "healthy", he was no more sick than he had been for the last year or so. He died 8 days later
It is my understanding that he left considerable notes and outlines, and that his wife who has been his editor and very close to him in writing the series will complete the final book. Because he knew of the disease and the possibility he would be unable to finish the series because of his diminishing health, he did make plans for this situation. The book was due out after the holidays so it must be mostly completed.