I've read What If?, the Australian one. Ranges from interesting (parliamentarians not paid until after Federation, a model Aboriginal state set up in the NT, Arthur Calwell assassinated, Whitlam re-elected in 1977) to fanciful (Tasmania becomes French, Australia's baptism of fire occurs at the Cocos Islands) to just plain silly (Australia becomes independent in 1908, on a policy of retaining White Australia against British opposition, and...becomes Japan's strongest and most steadfast ally, to the extent of adopting Japanese as a second national language? Wha?)
The New Zealand one looks really interesting; I'll buy it if I see it.