Collections of primary texts in anthologies can be good for browsing. They touch on many different issues, often excerpting brief passages from full works that you can find in the tricolleges or through interlibrary loan.
There are some online collections available for medieval texts. Haverford has access to Early English Books Online (EEBO). Other primary source collections like Gallica from France's Bibliothèque national are open access on the Web.
Still other sources are available in modern printed editions. Like these titles available in the tri-colleges:
A child and a monk fall victim to the plague as Pope Gregory I ( 590-604 CE) invokes God's protection
Illumination in the Très Riches Heures du Duc de Berry, an early 15th century prayerbook, fol. 71v (Wikimedia Commons)