Recent years have seen a considerable increase in the value and hence the prices of first edition New Zealand military books from not only the World Wars but also from other conflicts stretching back to the Maori Wars.
Many people buy for pleasure, but there are some who invest in these books for profit. As an example, Trench Mortars sold for approximately NZ$800 only 5 or 6 years ago, but recently has traded for well over NZ$3500. Whilst this is the extreme example, many other histories have seen a similar rate of growth in value.
Some collectors concentrate on specific publications - troopship magazines, postcards, soldier's diaries, whilst others just on the official histories. Investors are now doing the same.