When I first bought the intense course in Tongan I was not aware that it required a book to be read along with it. I received it in the mail and thought "how on earth do I understand the meanings of these sentences and words they're teaching me?"
With great luck, or divine intervention, my Tongan house-mate gave me a book, completely unrelated to the intensive course. The book happened to be the one that accomodated the course. What a coincidence.
4 stars because it is the only course available, but it is very good. Do it all and you'll be able to communicate with the Tongans in their language more formally. At this level you'll quickly pick up the local jargons and slangs and become a fluent speaker in no time at all.
I left off 1 star because it is not sold with the book....