Over the past few years, I've been noticing that when I want to learn about something (whether that be about PHP, CSS, WordPress or any number of other topics), that my tendency is not to turn to books anymore, but rather to check YouTube.
As a learning tool, I've found YouTube offers a platform that is tough to beat. It seems like no matter what it is, there's somebody on YouTube that's talking about it. What's more, the information is readily available and free.
If the topic is complex, such as in tutorials with detailed code examples, I can play the video as many times as necessary or even download it to my computer. Seeing and hearing somebody go over a problem in a video is a great way to learn. The voice of the YouTuber goes straight to that part of your brain that learns best when spoken to.
That is not to say books are obsolete, but they're a lot more work than watching videos. The goal is information. How that's transferred used to be primarily by print. Today it's video.