One of the most interesting parts of the book is the chapter “Tools for the Transition” Greer has a most interesting discussion of the merits of the slide-rule over the pocket calculator, and explains why it is infinitely more suitable to a low-energy world:it is durable- a solid aluminum slde-rule could last nearly geological time-scales-, independent, dependable and perhaps most significant of all its use of transparent- a future archeologist would be able to work out exactly how to use it. I have never actually used a slide-rule, but this discussion has inspired me to get one, and even teach its use on permaculture courses as an example of durable technologies. There are many other insightful observations Greer makes in this chapter, including comments on salvage and organic agriculture, and what will endure into the post-collapse world.