Hesse’s personal library and his literary remains were divided between the Marbach Archives (Deutsches Literaturarchiv Marbach) and the Swiss National Library (Berne) in 1964. The Hermann Hesse Archive in Marbach contains 6725 volumes: nearly all publications of the German author, including translations, secondary literature and parts of Hesse’s personal library. The Swiss National Library owns manuscripts, letters and personal property of Hermann Hesse, for example his spectacles or his type writers (with the italic letters Hesse very often used). Both archives can now be browsed online.
University Library (Basle): 300 letters by Hesse and the "Dossier Hermann Hesse" by Martha Ringier
Solothurn: Hermann Hesse Collection Rosa Muggli-Isler with first editions, private printings, newspaper articles, 263 letters and postcards by Hesse
Vadiana St. Gallen: Collection Max Thomann-Vonwiller (manuscripts, letters, postcards, pictures, photograhs)
Winterthur: Collection Georg Reinhart (letters)
Zurich (Library of the Swiss Federal Institute of Technology): Collection Alice Leuthold-Sprecher (Manuskripte, Briefe, Einzelausgaben)
Hermann Hesse Bibliography by Jürgen Below
International Hermann Hesse Society - Internationale Hermann Hesse Gesellschaft e.V.
Hermann Hesse Portal