Mark Rosenfelder. Advanced Language Construction. Chicago, Yonaçu books, 2012.

The sequel to the Language Construction Kit: learn more about constructed languages and about linguistics: logic, pidgins and creoles, sign languages, the linguistic life cycle, and a meaty step-by-step survey of morphosyntax. Create detailed and plausible languages for RPGs, fantasy and science fiction, movies, or video games... or just learn more about how languages work with the same accurate yet fun approach as the original LCK.