What do I need to read to be a great at CSS?

I think this is good advice:

A rule of thumb is that the importance of a blog in your feed reader is inversely proportional to their posting cadence. Prioritise the blogs that post only once a month or every couple of weeks over those that post every day or multiple times a day. You don’t want to miss a new Ahmad Shadeed post but there’s no harm in skipping the CSS-Tricks firehose for a few days. Building up a large library of sporadically updated blogs is much more useful and much easier to keep up with than trying to keep up with a handful of aggregation sites every day.

I used to subscribe to many web-related publications, never fully keeping up with their firehouse of a publishing schedule. But they did expose me to individual writers who I’ve harbored in my RSS feed for years.