Using ebooks at an academic library is different from using ebooks you bought or ebooks you borrowed from a public library. The ebooks in SU's collections are hosted on several different websites (platforms), so what you are allowed to do with an ebook depends on the platform where it is hosted as well as restrictions from the ebook's publisher.
When possible, read the ebook through your browser or download specific chapters rather than downloading the full book.
If you will need to read an ebook while you are not connected to the internet, you may need to check out and download the full title. In that case, you will need to create one or two personal accounts:
You will need to remember these logins and use them to access the book on a different device.