Perhaps select a specific time (e.g. year or period) and elaborate on an aspect of the topic after a general introduction. Eg from your 30 percent done and your broad overview, can you identify from the various contributing factors, one factor that would benefit from further elaboration and/or a period of time that relates to this factor in general? Then once you have given your general overview (in the intro chapter), your lit review and research would be focused on this factor and its influence over the whole topic.