Suggestions for more advanced books

Hello. A year ago, I purchased 1) Learning PHP, MySQL, JavaScript, and CSS, 2nd Edition
2) Learning Web Design, 4th Edition and 3)WordPress: The Missing Manual. Great learning tools. I would like to purchase books which go beyond these. I am now working in Wordpress and wanting to learn more about how to customize themes, learn more about CSS and HTML.

I have about $150 to spend on books. Would you be willing to recommend books in each category which I could read up on and purchase?

1 person has
this question