You can learn all aspects of web design and development online and for free, but for really getting to grips with a subject I personally don’t think you can’t beat a book. The photo below is of my mini library built up over 3-4 years, some of the books have seen more use than others, HTML By Example was the first web design book I bought and although much of it is now outdated (and probably not recommended) it did teach me how to build my first ever site. The more recent purchases are on the right and reflect my current interests CSS, usability and SEO.
If I was to recommend 4 of these books they would be -
I am always on the look out for new web design and development books and would be interested in any recommendations.