I say that he never did die, even though the novel says so, but that he severed his connection with the force; hence the force blast that occurred. By doing so his presence in the force would not be possible to detect (Yuuzhan Vong ring any bells) which is why the two dark lords thought he was dead.
There is no emotion, there is peace.
There is no ignorance, there is knowledge.
There is no passion, there is serenity.
There is no chaos, there is harmony.
There is no death, there is the Force.