The Letters of Abelard and Heloise is wonderful and completely evergreen since it's about love and broken hearts.

Confessions of St. Augustine is from late antiquity but I think should "count" as medieval because it was so influential to scholasticism, and is similarly great/relatable.

The Travels of both Marco Polo and Ibn Battutah (rough contemporaries who were active toward the end of the medieval period in the fourteenth century) are both fascinating and entertaining tours of the Mediterranean, Middle East and Asia.