Okay, maybe not all epics. But really, really long!
Argonautica by Apollonius Rhodius: Part 1 and Part 2. (Prose translation by M.A. Seaton.) Take to the high seas for adventure and romance with Jason and the Argonauts! If you’ve only read the barebones synopsis found in mythology books, you haven’t heard the story at all.
Gerusalemme Liberata (Jerusalem Freed), by Torquato Tasso. (Translated by Edward Fairfax.) The knights of the First Crusade have come from all over Europe to free the Holy City from oppressive occupation forces, while from throughout the Muslim world its warriors arrive to fight a jihad. But in this Italian poem inspired by Pharsalia, the Song of Roland, and the tales of King Arthur, both sides also send mighty champions, wizards, and supernatural forces into the fight. So take a listen — Deus lo vult!
The Parliament of Fowls, by Geoffrey Chaucer. The birds meet every year on St. Valentine’s Day to pick their mates. But this year, the male fowls all want the same chick, er, bird, er… female avian. Which doesn’t make Mother Nature happy.
Pharsalia (aka The Civil War) by Marcus Annaeus Lucanus (aka Lucan). You knew about Julius Caesar’s little tiff with Pompey, the richest guy in Rome (and Caesar’s in-law). But you never realized what kind of blood, gore, ghosts, and witches were involved! Written by a guy who was friends with Nero, and thus found out a bit more about horror than he wanted. Ends rather abruptly in Alexandria, because Nero suddenly decided Lucan wasn’t his friend. (Translated into English by Sir Edward Ridley.)
The Bridal of Triermain, by Sir Walter Scott. A medieval knight dreams of a lady from King Arthur’s time, and sets out to save her.