Our goal with the reading assignments was two-fold: (1) Match up the sections of the content review books as closely as possible with the video playlists, and (2) Include every single section of the content review books. Because some sections of the content review books didn’t match up well with any one single lesson, we had to put them into a random lesson (typically one that didn’t have a very long reading assignment). You can find more details on this process here.