Surprisingly good. I was a little put off by the search for *ahem* purgation early on, but the overall Okrent's style won me over.

Her chronological survey of invented languages was a fun trip - I enjoyed the breadth of languages covered, as well as the background discussion on their reasons for existing, the motivation and actions of their creators, and how and why they failed as languages.

Good pacing, about the right number of examples, and a varied-enough selection of languages and language styles to keep me eagerly reading. I especially enjoyed learning more about Klingon, something that I would've written off as a toy language, but as it turns out one that's had as much thought put into it as many so-called serious invented languages.

Recommended, if you've any interest in languages (invented or not).