There are some really good New Zealand road maps on the market that will be useful for you to buy at the planning stage of your holiday, particularly useful if you are travelling in a hired car or campervan rental.
You don't really want to have to spend any of your precious holiday time browsing bookshops looking for a map when you are there and should actually just be relaxing and enjoying yourselves.
Here are two maps that I have personally used and would recommend.

Kiwimaps New Zealand Travellers Road Atlas
All classes of road are indicated from Motorways and state highways to scenic routes, regional roads and 4WD tracks, and on the larger scale regional maps even road names in rural areas are included...
62 pages ...

Kiwimaps New Zealand Compact Travellers Road Atlas
New Zealand Touring and Main City and Town Centre Maps
A superb, easy-to-use road atlas. The principal mapping of the whole country covers 51 pages ...
Visit The Nile - New Zealand's Largest Online Bookstore and type New Zealand Road Map into the search box.
Or
ziwi.co.nz another great NZ online bookstore
Return from New Zealand Road Maps to the Explore New Zealand home page or visit my pages on NZ Track Maps, NZ Maps and Books, and Map of NZ