Your immediate next steps will of course be to make sure that you complete a couple of the suggested exercises at the end of this and the earlier chapters. There really is no better way to reinforce learning than by doing; take a cue from our learning agents. If you have time, look to build on or use another new example using ML-Agents.
Outside of your learning and this book, you have just begun a journey in a new wave of programming. It would not be surprising that in the near future (25 years or so) that programming becomes a lost art. After all, would you rather write a bunch of code or write an agent that writes your code better, faster, and even automatically has it tested? Yeah, no contest really. Therefore, if you are under 30 and reading this book, don't plan on programming for the rest of your life, look to teaching the programming agents.
With that in...