I totally agree. A good book that introduces CSS in a methodical perspective is a must. I personally cut my teeth on CSS with the book Web Design in a Nutshell, a 2006 book. I remember having written CSS in a haphazard try-and-see fashion before that, which utterly confused me, and then reading an actual book made everything clear. This is an investment worth making. Many years later I'm still almost always "the guy" on my team to go to when there's a weird CSS issue.