Specifically how do you add onto your introductory studies?

May 2019
Lets say you're diving into a new topic and using a single book to start off on this historical period would you first write notes on the subtopics presented in the book first and then once finished add onto each subtopic with individual research from other secondary and primary sources or would you add onto each subtopic before you start the new one?

Example: I'm currently studying the Ancient Near East and using A history of the ancient near east (marc van de mieroop 2015, v3) as my introductory secondary source on the topic. I'm currently planning on doing notes on each subtopic presented in the book as I go. For Example I have done my own summary of the preface presented in the beginning of the book on the general geography of the region and the prehistory (10000BCE to 3000BCE of the Ancient Near East) but I'm wondering before I go to the next subtopic of city states should I first use other sources to widen my knowledge on my current subtopic of general geography or should I just summarize notes for each section of the book then once finished broaden each subtopic one by one from the beginning?

Hope I'm not confusing :p