NZ is great, you'll love it. Lots to see on both North and South Islands. The guidebooks probably cover most of the standard stuff, some good. "Lonely Planet" series is about the best for low-budget stuff.
Near Auckland, out on the Coromandel Peninsula, and north around Bay of Islands is spectacular. Rotorua is cool, too, but can be touristy.
Kiwi pubs have great beer on tap, and, check out the bath houses (if you're travelling single), they're probably not listed in the Michelin guide.
Have a good trip, I'm jealous! Cheers, mate!