Popular and undergraduate histories were much more academic in style decades ago then today. I had trouble focusing on this in part because I spread my reading of it out too long and part because it covered so much territory (literally and figuratively).
Like other books in this series, this one is not for the faint of heart. It is a scholarly, college-level survey of the period. Slow reading, but well worth the effort. If I can remember a quarter of what I read I'll be doing well.