Complex sentence: The accompanying text is mostly a running commentary on what the maps show, and is another feature of the atlases, being written in McEvedy's witty and engaging style with which he often made reasoned challenges to established opinion among historians and demographers.
Split into simpler sentences: The accompanying text, typically, is mostly a running commentary on what the maps of a given atlas show. Another feature of the atlases is McEvedy's witty and engaging writing-style, with which he often made reasoned challenges to established opinion among historians and demographers.