It's not uncommon for history books, textbooks in particular, to have chapters that are subdivided into sections organized both topically and/or chronologically. When a chapter is broken down into sections, each section is usually identified by a boldface heading followed by a blank line, or by using boldface text for the first sentence of the paragraph. Quickly reading the section headings before jumping into the body of the chapter will give you a better understanding of the main idea(s) that are presented in the chapter. Again, remember, as we pointed out previously, you want to develop an understanding of the big picture first and then work your way down to the detail.