Pro jQuery interested me for a variety of reasons. jQuery itself has been a technology I've wanted to get stronger in since I've seen it in action. It is amazing how widely adopted it is in 2012. Even Microsoft has started embedding it in their template project start ups.
The first chapter talked a little bit about jQuery and node.js. It was a lot of the typical first chapter stuff such as downloading the source code, browsers, etc. There wasn't a lot there that I found to be too useful. node.js though, I'll need to revisit. I didn't fully understand what it was, how it is used, and what I need to do to get it running. I understand that it is a server side technology, which surprises me, but based on what I read about it, it is a widely accepted tool.
The second chapter was an HTML primer. There was a lot there that was just a lot of technology I use in my day to day activities. Things like element hierarchy, inputs, and the DOM are common day to day tasks in the life of any web developer.
The third chapter was a CSS Primer. I really just kind of flipped through this. I feel I have a strong handle on CSS (or strong enough for now) that I didn't really need the primer. I still looked at it though and made sure I understood all of the concepts on there. It was interesting to me to find the section about Selecting by Relationship. I've seen and used most of these, but there were a few that I had not ever seen.
With the exception of node.js, the first few pages were primer to anyone who has used HTML and CSS. jQuery information was in there, but it was very generic, and most developers already know a little bit about it in terms of what it is, where to get it, and the different things you can do with it.