Assuming you are particularly interested in European history between the 410 Sack of Rome and the Italian Renaissance, one idea to contend with within the bigger picture is "continuity versus collapse." Meaning, what degree of credence is there in the narrative that the period was "dark" related to intellectual output and cultural significance? There's been a lot of reconsideration over the last century to evidence that this period was rich, intriguing, and worth historical study.

A book that is scholarly but written for a general audience is The Middle Ages, by Morris Bishop, the Cornell historian. It's approachable and can provide jumping off points to read other primary texts and lead to seeking out other authors on more specific topics.