David Graeber, Debt: The First 5,000 Years (2011). Not strictly speculative fiction, but a representative of all that "the truth is stranger (albeit less rigorously extrapolated) than fiction" anthropology out there. Jo Walton remarks in her review ("The Best Science Fiction Ideas in Any Non-Fiction Ever: David Graeber's Debt: The First Five Thousand Years") that a problem with writing SF and fantasy "is creating truly different societies. We tend to change things but keep other things at societal defaults. It’s really easy to see this in older SF, where we have moved on from those societal defaults and can thus laugh at seeing people in the future behaving like people in the fifties. But it’s very difficult to create genuinely innovative societies, and in genuinely different directions." Graeber's book is also a great reminder that many well-known facts (such as the fact that money was invented as an improvement over barter, solving the double coincidence of wants problem) are liable to reveal themselves as rather wild and far-fetched speculative fiction. You can also check out Graeber's 2009 article for Mute which condenses a few of his book's major arguments. And also see Graeber's On the Phenomenon of Bullshit Jobs, which talks about something that several speculative fiction writers have noticed (Douglas Adams is one of them).
Still the best book about money I've read.