Somehow, the meaning of The Last Days is not quite locating in understanding its plot, which is told through a mystery lens, enticing the reader to do just that. But actually in the end, the real thrust of the novel has almost nothing to do with the plot, but rather, the characters. The novel is really about death itself, shown first in the wrongful, untimely death of a grandson, and then ultimately, the death of Ptolemy himself.
By making Ptolemy deal with a death external to himself, during his last days, Ptolemy is able to make an existential decision in response to the basic facts of the situation, that his family man is dead and that death is coming for him next. The violent end of his life is like a proclamation, like the poet once said, "Do not go gentle into that good night." The decision to regain his mind at the expense of his longevity was not a difficult decision for Ptolemy, another indication that he has enough life experience to stare straight into the prospect of death, and he brings judgment against death in his anger.
It's more fundamental than the plot indicates. Some novels are designed to be entertaining, and some novels are designed for more particular goals, and one gets the sense from analyzing The Last Days that what is really going on is that Ptolemy is being forced to analyze his own death from a third person perspective, so if the novel communicates a horror about death and the finality of death, the novel has succeeded.
