As far as supernatural beings go, trolls have not been done to the extreme in fiction - at least, not yet.
I also know hardly anything about troll lore, other than a few fairy tales, the most notable being The Three Billy Goats Gruff. So it's difficult for me to decipher how much of the mythology of this book has already existed and how much is due to the ingenuity of the author. Either way, the ideas espoused are fascinating.
The writing, on the other hand, is pretty horrific. This novel was previously a bestselling self-published e-book, and the author gets my kudos for successful marketing and sales, but not for craftsmanship. As I've previously stated, the ideas are terrific; the writing, however, is simply not good enough to make the ideas shine.
My verdict: pass on this novel, unless you are only interested in the plot of a novel.
(Switched is slated to be released in early January, 2012.)