So I just copy/pasted the book recommendation into search, and the first result was a pdf of the entire book hosted on an edu server. Forgive my ignorance, but

So I just copy/pasted the book recommendation into search, and the first result was a pdf of the entire book hosted on an edu server. Forgive my ignorance, but would this be a pirated copy or something? This often happens when I'm searching for book recommendations like this and I just assumed older versions were pushed out into the public domain or something.