Cause that's it's reputation in math circles. And recommended by most of my teachers. Also because I used it a lot. You don't need to read it top to bottom. I t

Cause that's it's reputation in math circles. And recommended by most of my teachers. Also because I used it a lot. You don't need to read it top to bottom. I think people here are interested by monoid and stuff. But to do the monoid part you don't really need category. An Algebra course about monoid is good enough actually.