A great fun and funny look at the history of some of the bigger-name invented languages, what makes them work and not work and who were some of the personalities behind them. Okrent is a linguist, so she actually gets involved with some of these languages, tries to pass a Klingon proficiency tests, attends an Esperanto conference. She has a good sense of humor about a lot of this but also bring s a lot of good background knowledge to the topic, so her takes are well worth reading.