From the Jack London Museum at Jack London State Park: a collection of First Editions! Jack London wrote fifty books during his short career.
Like many writers who actually depended upon actually writing to support himself, he dreamed of not having to be a "scribbler". Thus, at the conclusion of his life, he schemed many different ways to avoid sitting down with pen and paper. He started a farm. He started a Grape Juice Company. He had a winery. He had other ventures which promptly went belly up. All this from a Socialist (some say he backed away from this position at the end of his life--I'm of the opinion he was more like the Nearings and withdrew to a rural life; his Socialism was more of a reaction to Industrial Society).
Valley of the Moon is the valley that includes Sonoma and Glen Ellen. I took a brief visit to Jack's home after work on Sunday. Only had an hour to take in the major attractions, and I chose unwisely... This is the news paper announcement of his death.
We sanitize heroes deaths. The State Park listed it as "kidney failure". Probably true. But a biography from 1964, I think gets it right. Jack being a man of non-soberisity (he drank like a fish)--and living in a hot environment...suffered kidney ailments. Specifically, kidney stones.
Discovered next to him in his "sleeping porch" were a couple bottles of morphine. He suffered from chronic kidney stones (I can relate, having had one once).
The theory was that he was in pain and took way too much morphine. The kidney stone didn't pass and he died from both a morphine overdose and kidney failure: uremia.
If you've ever had a kidney stone, it is easy to see why he would take too much morphine. When I had mine, I was frightened I was gonna die (from the pain); concurrently, I was frightened I wouldn't die (because of the pain). This explanation makes sense to me.