HathiTrust is a collaborative effort of academic libraries around the world. In cooperation with Google, Internet Archive and others, earlier works are digitized and made accessible - as far as copyright law permits. Currently, around 20 million works are indexed at Hathi Trust, 5 million of which are accessible.
In HSGswisscovery you can find and access 5 million works that are in the Public Domain. These works can all be read online.
If you search via https://www.hathitrust.org, you can search the entire collection, but access is still limited to ¼ of all available documents.
The HSG-Library is not a member institution. Unfortunately, a HathiTrust participation outside the USA makes no sense (so far).
Download functionality: for the vast majority of available works, only individual pages can be downloaded, one at a time. An integral download is not possible. Please refer to the Access Chart on the page How to Search & Access – HathiTrust Digital Library.