Some are using a tool to get free books

This is a very popular website. Pretty much everyone I've known at university knows about library genisis. I've been using it ever since I was in my upper years of high school in order to get textbooks that might have interested me. Library genesis has many different links but the most prominent ones that I know of are https://www.libgen.is and https://www.libgen.rs , I think the link in OP's post didn't work because they forgot to add the www in the link
This site has saved me hundreds of dollars on textbooks and I have even uploaded my own pirated textbooks onto it. If you need to find a pdf of a textbook, libgen is one of the first places to look. I love that website.