This article briefly details the strange hotness of posthumous works. I've noticed for some time that for America in particular, for some reason, being dead significantly drives up one's literary cachet. So John Kennedy Toole's novel A Confederacy of Dunces, for example, which couldn't get published during his lifetime, became a literary best-seller after his suicide.
I can think of far more examples, but the most prominent and recent one (and well-deserved, I might add) is Roberto Bolano. I will write more (much more) about Bolano, as I think he deserves all the hype he has received from the literary establishment in recent years. Here, though, I will only say that it is interesting that, while he was certainly published and somewhat known in life, it is incontrovertible that Bolano only became "Big" in America after his death. And I would argue that it was his death, along with the (now disputed) image of the drug and alcohol filled haze that led to it, that greatly helped exacerbate his fame (which is very well-deserved, I must emphasize again) and catapult him to literary stardom.