I will nominate two works to be read together as one nomination: Letters
by Heloise and Pierre Abelard and Historia Calamitatum
by Pierre Abelard. I group them because they are relevant to each other and are both rather short.
The story of Abelard and Heloise remains one of the world's most celebrated and tragic love affairs. Through their letters, we follow the path of their romance from its reckless and ecstatic beginnings when Heloise became Abelard's pupil, through the suffering of public scandal and enforced secret marriage, to their eventual separation.
Letters are their letters to each other, while Historia Calamitatum is Abelard's autobiography of sorts.
ETA - To give a little more context: They lived in eleventh and twelfth century France, and Abelard was a promising intellectual of noble descent while Heloise was a nun with a renowned intellect.