Books you should read:
The road to becoming a successful web developer (not just designer) can be a long one, unless you know where to look to make it shorter. You should never stop expanding your skills and knowledge. That is why I recommend you read the 3 books above. The first 2 will help you become comfortable using HTML and CSS for creating static websites. The last book (PHP MySQL Web Development) will help you become familiar with creating dynamic websites. Such websites are popular so in many cases knowing only HTML may not be sufficient.
I want to repeat what I have pointed out earlier the sooner you become the All-In-One solution for your web design clients, the sooner you will be making a lot more money. You need to be fully comfortable coding websites and editing customizable templates and WP themes. You need to have a lot of traffic to your website in order to have clients. Read books that teach you how to build websites using HTML CSS and learn how to use PHP and MySQL. Of course you should also read my tutorials 🙂
If you follow the steps in my guide, you will not only design websites for your clients, but you will also be able to Sell hosting. save a LOT of time by not designing from scratch, get many more clients by building more traffic to your site, and make thousands of dollars per month by selling SEO services to your clients. The sooner you start taking action, the sooner you can be earning a lot more money.