Friedrich Nietzsche: Thus Spoke Zarathustra — written in Sils Maria across several visits in the 1880s. Nietzsche said the ideas came to him on the walks around the peninsula lake, and the alpine landscape is present throughout the text. Read it in Sils Maria; it makes more sense there.
Robert Walser: The Walk — not set in the Engadine, but the Swiss German writer who walked obsessively through the Alps produced something essential to understanding the Swiss relationship with landscape. His notebooks from winter journeys in the Graubünden are compelling.
Giovanni Segantini — the painter who died near the Maloja Pass in 1899 left diaries and letters that document the late 19th-century discovery of the Engadine by artists and intellectuals. The Segantini Museum in St. Moritz holds the major work and the archive.