Regarding PDF copy of a book downloaded from reputed universities For ethical reasons I try to avoid reading books downloaded from illegal and pirated websites.
I was self studying a topic by reading a certain book. Due to COVID-19 my nearby library is closed. I googled the book's details and I came across the full PDF version of the book on the websites of two reputed universities.
Is it it unethical to read the PDF downloaded from a university website? How the university is able to upload the PDF? Will it be unethical if I read from the PDF downloaded from the websites of these reputed universities?
Please help me in overcoming my confusion.
If a reputed university has uploaded the PDFs online, chances are they are legally allowed to. This could be, for example, if:

The book's copyright has expired.
The copyright allows for distribution (e.g. if the book is open access).
The copyright holder allowed the book to be distributed.
The university paid for the right to distribute the book.

So it should be OK for you to use it. If you're still worried, look at the license statements that come with the download.