Reading for world-building is a skill. I have seen brilliant people, laureates, inventors, Ph.D.s, try to read fiction with deep world-building and fail completely, looping back, rereading, never following events, trapped in a sense of muddled wandering. Reading for world-building requires retaining information without context: a term, a place, a coin, a category comes up once and we know what that is — a puzzle piece — that our task is to gather up these pieces as the author drops them, and to slowly assemble the whole. This is not easy. Human memory needs hooks for facts: a mnemonic, a story, context, something; grueling textbook rote-learning fades quickly, but a story of the statesman or the king, that’s what makes knowledge stay. To retain puzzle pieces that don’t connect, dropped without context, is a skill that not all have. All had it once: it is how children read, every book, poster, and headline a stream of unknown terms, far too many to ask about them all, but the child retains them, trusting that they will connect to something someday. Kids collect Earth’s puzzle pieces every time they read, but as we move to grown-up books they all use the same picture, and define immediately those terms they fear a reader may not know. Thus the skill of keeping puzzle pieces fades, unless we read books set in other worlds, new puzzle pictures which make us retain the skill, as frogs sometimes retain their tadpole tails into adulthood.