Yep, I'm a native dutch speaking man, and although I already have a (rather good?) upper intermediate knowledge level of the English, French,... language, I'm still learning some new English words from time to time using RtK. Not that there are too many new ones, but still. I had not heard yet for example: Yonder, Fathoms,... coming from the first part of RtK.
It's funny to see how you can learn about two things at the same time
when you actually wanted to learn just one - big - thing. Even though that I already now most English vocabulary words from the book, it does help "refreshing" them. Aah, exposure, indeed sensei! 
I guess there are lots of other non native English speaking people using this English-Japanese book/method? There are just not enough 'non-english-language' <--> japanese books.
It's funny to see how you can learn about two things at the same time
when you actually wanted to learn just one - big - thing. Even though that I already now most English vocabulary words from the book, it does help "refreshing" them. Aah, exposure, indeed sensei! 
I guess there are lots of other non native English speaking people using this English-Japanese book/method? There are just not enough 'non-english-language' <--> japanese books.

I see it as an opportunity to learn an extra thing. But oh dear, I'm also happy there are free online dictionaries