Here's a topic that isn't often covered: how museums design their exhibits. You know what else isn't often covered: how science happens. There are myriad books about discoverers and discoveries, and many about new fields as they develop. But this is the only time I can recall reading a book on the evolving science behind an issue like Is Pluto a planet? And although the book isn't specifically targeting a young readership, I think it could be wonderfully popular with middle school readers, because 1) Neil deGrasse Tyson is amusing 2) he is very good at explaining things, and 3) students are featured commentators.
I'm not going to try to summarize the book, because it's a quick read, and highly enjoyable, and is itself a summary of more than a hundred years of astronomy. I loved it, as did my middle-school child who wants to design robots for NASA one day.
Word of warning, though: don't read the absurdly long photo captions if you're actually reading the text.