The Symposium is a philosophical text by Plato dated c. 385–380 BC.  It concerns itself at one level with the genesis, purpose and nature of love, and (in latter-day interpretations) is the origin of the concept of Platonic love.
This is an interesting book with some points about love I never considered prior to reading it. The layout and behavior of the characters seems to indicate or demonstrate what the points made in the text appear to us as in real daily life.
A very interesting and impactful read on the subject of love as seen by Greek thinkers. Contrasts very well with current thoughts of love!