A language course book for learning Dothraki(!)

[Eddard Stark is online]

I was just browsing the HBO merchandise website when I came across this book: Game of Thrones - Living Language: Dothraki

Essentially it teaches you conversational Dothraki, and even includes a 1 hour CD with exercises to help you with pronunciation, etc. The linguist in me is going crazy with excitement at this. Is this the arch geekiest spin-off ever, or super cool? (or both?) Damn it, I think I'm gonna buy it!! :laugh:

Another thought: Is it worth the effort to learn (of course it's just for fun) a made-up language that only appears in the first book, or do you reckon it's worth holding out to see if they do one on Valyrian (or another language that features more prominently)?