These are all books that I own, read, liked, were helpful, and that I recommend.
This would be a good choice for your first ever book about web design. Especially if you are just getting into it and are into building sites from scratch. You could even teach a class from it, as it reads like a curriculum, each chapter building on the last and providing quizzes at the end to test your knowledge. Despite being for beginners, it covers the latest best practices including designing for small screens.
This is an incredibly well designed book. And shouldn't it be? Just as HTML & CSS are all about content and design, so too are books. Stands to reason a book should practice what it preaches, despite the different formats. The examples in the book look great too, which, to me, isn't just a nicety but vital to learning. Just as learning the guitar is a lot easier when you learn with a song you like, learn web design is easier when you build beautiful things, not just aesthetically bare "concepts."
This is the best of it's kind at teaching you what it is to be a CSS developer. It covers using CSS3 as progressive enhancement to do very cool things in modern browsers and perfectly acceptable things in older browsers. Dan has a casual-yet-masterful style full of humor and can't miss information.
Donald intentionally doesn't use computers or the web as examples in the book, but every concept presented has clear connections with web design. How do you know how to operate a device when you've never seen or touched it before? It's because of affordance. In other words, things do what they look like they are going to do.
This book is the answer to the question: "I want to buy a book just about CSS." It's the best book that tackles the technology of CSS. It explains what you need to know to understand how CSS works and can be read straight through, or as a reference guide.
Does something as niche as the design of web forms deserve its own book? Yes; yes it does. Forms power the interactivity of the web. They are absolutely everywhere and they stand between us and doing what we want to do on the web. But all too often, the usability of forms sucks.
Maybe you "get" responsive design. It's all about fluid grids, and media queries and making things fit. But there are about a million things that can go wrong or stand in your way of doing that right, starting with your very approach to the project. It also gets into how your server can help. RWD doesn't need to be exclusively a front end endeavor.
Ofter referred to as the bible of typography. It is an entertaining read, despite tackling some tedious and, by most regards, boring material. There is no lack of practical information here. You will be given plenty of do-this don't-do-this information that will certainly make you a better typographer. The best part of the book how it eats its own dog food. Almost every example is perfectly weaved into the layout of the book itself.
It's funny that we need a book like this, as web designers, to remind us to use our own common sense when designing. There are so many patterns that get ingrained into us on how websites work that we often forget simple things that would make life for our visitors so much easier. This book is short and sweet, just like a good user experience!
This book is loaded with helpful advice about typography. It gracefully talks about type in print form and web form, which is welcome. My favorite parts about this book are the examples where Ellen takes a bit of content and lays it out in many different ways so you can see how each feels and how they are different from one another. That, and the "type crimes" scattered throughout the book, which are both funny and helpful.
Where Don't Make Me Think talks about web design in general, Designing the Obvious focuses on web applications. Robert is an experienced master of user interface in web applications and this book does a fantastic job of sharing practical advice in making yours better.
I put Karen McGrane's book "Content Strategy for Mobile" as the image as it's a fantastic read, but I endorse the entire collection of A Book Apart books. They are nice and short as well as timely and timeless.
A shameless plug for my own book! Jeff Starr and I take an intermediate-level look at WordPress and what it can do for you. We cover everything from setting things up right, to theme building, to using WordPress as a CMS, to SEO and maintenance best practices.