Appendix A (Resources) contains a list of great books that I can recommend for further learning. Each of them treat a specific topic, so I would recommend you to start with something that is of interest to you, whatever you liked more from what you've read in this book.
Writing code is the best way of improving your skills as a programmer. If you do not work yet in this field, you should consider creating a few (small) projects. Small projects are a good way of showing to a potential employee that you are determined to have a career in this field and that you are actively working on improving your technical skills. If you already work in the field, projects will show to them that you are passionate, and will improve your knowledge over a particular area or with a specific programming language.
You need to develop your programmer mindset / mentality. First of all, you shouldn't focus on memorizing the code syntax and such, that usually comes with practice. Secondly, I want you to not cheat yourself and the process. When you encounter a problem and/or get stuck, the easy way out is to find for answers on the internet, but that will not improve your thinking, will only make you rely on the internet and/or others.
,,There is no shortcut to seniority - There is only hard work!