It's coming out in September in Canada, although I suspect import copies will be available at places like Bakka well before then. Amazon.com doesn't currently list a release date in the US, but it'll make it there, never fear. The first two books have, after all.
(I was inadvertantly reminded of this forthcoming event because Glosses recently posted on the first book. As did theengineer, who ran a discussion on it for a book club he's involved with.)