I'm reading Peter and the Starcatchers by Dave Barry and Ridley Pearson. It covers the back story of J.M. Barrie's Peter Pan. Tomorrow's project is to learn about all the various permutations of the Peter Pan story (if there are any others).
I'm at the end of the book, and one of the things it introduces is how fish became mermaids. Interestingly, reading an article on SLATE today, I saw this headline "Why Animal Planet’s Fake Documentaries About Mermaids Are Dangerous"