At this stage you are well on your way to shell mastery. Each of the chapters in this section goes introduces either an advanced technique to help you be more effective in the shell, or goes considerably deeper into one of the topics that we have already covered so that you can really understand the fundamentals.
Depending on the kind of work you do in the shell, you might find some chapters more useful than others. For example, if you are a software developer you might find the chapter on 'Makefiles' of particular interest, and if you administer remote systems, you should definitely read up on 'Multiplexers'. Feel free to dip into this section of the book in the order that suits you or that you find the most interesting!