My wife and I went to New Zealand in 2006 and used this book above all others as our major reference guide when we toured the whole of the south Island. Unlike a lot of other map/guide books this has stunning illustrations on every page and presents dozens of individual rad trips you can take around New Zealand, both north and south islands.
In short, this book is so good it had native New Zealanders singing its praises when we passed it round and shared discussions of our travels when we finally met up with friends and relatives in Wellington. If you're going on a road trip to New Zealand for the first time I'd recommend this book as it reveals quite a few routes you may not otherwise pay attention to. Good value.