Surviving Death, and won't try to summarize or systematically wrap up--it's all too complicated for that. But maybe you'd like to know the punchline. It's that even without supernaturalism, we can reasonably believe that death is not as bad for the good. Basically, for two reasons:
(1) The good know that other people's cares and feelings are objectively as important as their own. So they know that when they're gone, what remains will really matter and still (often) be very good. They can content themselves with the thought that life will go on, and undiminished. In contrast, the bad think their own pleasures are all that count, and those pleasures are undoubtedly extinguished by bodily death. So death for them is especially appalling.
(2) More strikingly, Johnston argues that the good can reasonably think they won't really be wholly absent from the world, after their bodies expire. They will survive "in the onward rush of humanity." All of the book's explorations of personal identity are preparation for chapter 5, which offers "a new refutation of death."
It's not fair to criticize without first explaining, and time/space doesn't allow. So take these comments with a grain of salt, and read the book if you want to really understand Johnston's theory. But here goes--
Johnston bends over backward to eschew any kind of supernaturalism in this book--there are to be no supernatural deities or souls in this "rational reconstruction"of religious beliefs about goodness and death. My feeling is that he trades in supernaturalism for a different sort of superstition.
The Hibernators are a critical warm up for the refutation of death in chapter 5. They don't believe in any science-resistant entities, but their view of the world is still profoundly irrational (in my view, not Johnston's). They think new people rise out of their beds after three months of hibernation, despite all of the physical and mental continuities that connect the "old" and the "new." Thinking this way doesn't make it so! That's what I'm inclined to think about the dispositions of the ultra-good that grant them a kind of survival after death--as Johnston explains in chapter 5 (and this does get tricky--so there's no substitute for reading it).
The (allegedly) death-defying attitude involves attaching exactly the same weight to everyone else's interests as to my own. The contrast with supernatural Christianity couldn't be more stark. Today's "Christians on the street" think they can fairly egocentrically enjoy this life and still have more joy to come. What a deal! On Johnston's view, that's incoherent. You only get to survive in the onward rush of humanity if you "decenter" throughout life--make yourself no more than one in 6 (7, 8, 9.....) billion. I'm a little skeptical that Johnston has contemplated what that would really mean. The sacrifices would be enormous, and the survival thin (at best).
So...survival? Not convinced. I do think there's some truth in (1), though, and that it may even be palliative--a comfort to the dying.