There are many great hiking guidebooks for New Zealand including our top pick Lonely Planet Tramping in New Zealand.
Rather than compete directly against LP, a new speciality guide takes a different focus:
The reality for most New Zealand trampers is that their tramping often has to be fitted into weekends.
In recognition, Nick Groves, a leading New Zealand outdoor photographer, and now writer, has collected together the best of the South Island’s two or three day tramping trips.
These trips, selected from all over the South Island, range in difficulty to ensure that there are tramps for every ability. Essential information on length, grade, time, suitable maps, access and sources of information are provided for each tramp. This is followed by a more detailed description of the tramp and what you might expect to experience.
The book is heavily illustrated, with colour reference maps for each section and the author’s stunning photographs throughout.
besthike.com 
I have the North Island version of this book, and I’ve found it very handy. Yes, we usually have to fit our trips into two or three days, so it’s nice to have a whole book dedicated to the achievable! (The only problem is how long it would take us to drive to and from some of the tramps.)