The White Spider by Heinrich Harrer (1959). Harrer's account of the north face of the Eiger is the classic book about alpine climbing in its golden era — obsessive, lethal, and magnificent. Though not specifically about Zermatt, it conveys exactly the culture that produced the Matterhorn climbers and the disasters commemorated in the Mountaineers' Cemetery.
Scrambles Amongst the Alps by Edward Whymper (1871). Whymper's own account of the first ascent of the Matterhorn and the disaster that followed. Dry Victorian prose and extraordinary illustrations by the author himself. The account of the summit day and the catastrophic descent is one of the best pieces of mountaineering writing in the English language. Whymper never entirely resolved the controversy about what happened on that rope.
The Alps: A Human History from Hannibal to Heidi by Stephen O'Shea (2023). A wide-ranging history of the Alps as a cultural and political force, covering everything from Roman generals crossing mountain passes to the invention of alpine tourism in the 19th century. Good for understanding why Zermatt and the Matterhorn became such central objects of Victorian imagination.