18. Children of Memory (Adrian Tchaikovsky)
The third and presumably (but not hopefully) last in this series by my favourite author. What a finish if it is though - the hard sci-fi series takes a very interesting turn and the story here is more like a dark fairy tale or fantasy than the previous two installments. But holy shit, it's still dealing with the big issues that would face a post-scarcity interstellar distributed society. Amazing stuff.