When that BoingBoing review came out I added the following comment to the thread:

I'm not at all sure this is at all a realistic premise. If we are going to have technology that is that effective at preventing aging, then it shouldn't take that long to figure out how to use it to make the really old people younger. Moreover, without such technology the non-aging elderly people will die off a lot faster since they are in less healthy bodies.

Also, the risk of overpopulation and resource consumption would likely go down not up in this sort of situation. The primary cause of overpopulation is high reproduction rates, not high life expectancy. In most of the world, fertility goes down as lifespan goes up. One might think that this is due to the fact that longer life expectancies now are due in a large part to reduced infant mortality (which massively brings down the average), but this is still true if one looks at the life expectancy of people who have survived at least three years of age. So it is likely that having near immortals would make people reproduce even less.

So what would be the immediate results? Well, you all know how if a mathematician hasn't done great work by really young age then they won't ever do great work? And how in a lot of the sciences this is true for slightly older age? No longer a problem. All those great minds will stay young and healthy making new discoveries. And if anyone gets too bored in one science they'll see how well they can do in another one.

What about direct resource consumption? Well, there won't be anyone who is really, really elderly. The vast majority of medical resources that go into life go into two parts: when you are really young, and when you are really old. Even if the octogenarians take the cure they won't live long. After that, this will never be a problem again. So within a decade or two equivalent medical resources required per a person will go down a lot.

What about the consumption of gasoline? Well, that's certainly a problem, but that's a general problem that's really disconnected from the population problem. To some extent that's due in part to overpopulation, but even that's only part of the problem. Much more of that problem is due to American lifestyles and a lot of the world following on American lifestyles. That would need to change, but the truth is that society won't collapse if we need to add lots more public transit. A lot of Europe does that already (equivalent gas prices are much higher due to taxes) and they get along just fine. If anything, the scientists who now won't become old farts will have far more time to figure out replacements. I'm pretty sure that an immortal Steven Chu and an immortal Terry Tao can probably solve a lot of the world's problems given enough time.

Overall, this book sounds fun, but I don't think anyone should take away any sort of lesson about the dangers of immortality from it.

Overall, the amount of deathism in that thread is fascinating.