In the Land of Invented Languages by Arika Okrent is about artificially constructed languages. Okrent's style in this book closely resembles that of a travelogue. For several of the languages Okrent gives a little historical background mixed with a description of her personal experiences with the language in question. At times the material can be a little dry, it is linguistics after all. But don't let that discourage you because Okrent can be uproariously funny too.
I found the topic and Okrent's style so engaging, I read the book in a little over a day. I enjoyed it immensely, recognizing several of the languages she discusses. My only disappointment was that, at times, Okrent may have been a little too breezy. I would have enjoyed a little more background in linguistics and perhaps a more description of how the constructed languages she discusses worked.
If you don't know anything about artificial languages, Okrent is a capable tour guide. I would recommend this book to anyone interested in the geeky world of constructed languages, even if that interest is only a passing one.