Into the Heart of the Maukā by John McCraw is a natural history of the Southern Alps and the Canterbury high country, tracing the geology and ecology of a landscape shaped by plate collision, glaciation, and altitude. Not a thriller, but essential for understanding why the mountains look the way they do.
The Bone People by Keri Hulme won the Booker Prize in 1985 and is set on the West Coast and Canterbury region of the South Island. It is a demanding and extraordinary novel — dark, violent in places, deeply embedded in Māori culture and the landscape of the South Island. Worth reading before or after travelling the area.
Station Life in New Zealand by Lady Barker (Mary Anne Barker) was published in 1870 and recounts life on a Canterbury high-country sheep station in the 1860s with warmth and considerable wit. It remains one of the most readable accounts of early South Island settler life and gives context to the high-country stations that still work much the same land today.