When we speak of ancient Roman novels we are generally speaking of works of narrative fiction written in prose. By this definition the Aeneid is not a novel; it is an epic poem.

Ancient novels are typically classified by their language, so we talk about “ancient Greek novels” or “ancient Latin novels”. The Golden Ass by Apuleius is not the only Roman novel to survive in its entirety. We also have a nice collection of ancient novels from the Roman Empire written in Greek!

(Speaking of Latin fiction, we shouldn’t forget Petronius’ Satyricon, although some might not consider this a true novel because it mixes prose and verse.)

You ask what kind of stories they wrote about. It is really a rich and varied field, but here are some examples of genres:

Quasi-biographical fiction. We have examples of stories written about the lives of Alexander the Great and the sage / magician Apollonius of Tyana, for instance.

Pseudo-documentary. Fictional eyewitness accounts of the Trojan War were written by Dictys of Crete and Dares of Phrygia.

Fictional letters. There are a few cases of proto-epistolary novels, meaning a narrative constructed out of fictional letters. Dracula was written in this manner, if you’d like a more modern example of the form. Other examples are Aelian (letters from a farmer) and Philostratus (letters from a lover).

Christian narratives. This is a special category, because it can be argued that they were never considered as fiction in the same sense as these other works we are discussing. However, scholarship has shown that many early Christian narratives share themes and techniques with non-Christian novels of the era. These were not written in isolation but were part of the larger literary environment.

Love and adventure! This is the type of story that tends to immediately comes to mind when you think of an ancient novel. They often followed formulas, just like a Hollywood movie does today. Pirates! Mistaken identities! Rival suitors! Shipwreck! Separated lovers! Happy ending! They were thrillers and probably aimed at the educated classes for their light reading or entertainment.

To give a taste of ancient novels I will now give a few specific examples.

Lucian’s A True Story. This is always a fan favourite, because it is often called the first science fiction novel. It includes a trip to the moon, an interplanetary war, bizarre lifeforms and Lucian’s brilliant wit.

Longus’ Daphnis and Chloe. This is my personal favourite. It is about a shepherd and his love, separated by many mishaps and adventures before finally living together happily ever after. This novel is interesting because it is a bucolic novel, meaning a rural story about a shepherd. There was a thriving genre of bucolic poetry, but Longus took this idea and turned it into prose. It also has some serious erotic undertones. If this hasn’t been made into a porno yet I’d be surprised.

Alexander Romance. This was probably ancient Rome’s most successful novel and there are quite a few versions out there. It is a fabulous biography of Alexander the Great, sometimes including magical monsters and marvels. (Think Abraham Lincoln: Vampire Hunter.) This was told and retold into the Middle Ages, but when we think of ancient novels we normally think of the Pseudo-Callisthenes version which dates to circa 140-340 CE, although Pseudo-Callisthenes seems to have relied on some earlier books as sources.

Heliodorus’ An Ethiopian Story. This story is the typical adventure romance - with separated lovers, mistaken identities, bandits and a happy ending - but Heliodorus was a talented writer and was able to solve many of the formulaic problems of the typical romance. He used sophisticated techniques, such as starting in media res – at the scene of a slaughter, no less – and an impressive sense of how to build tension and drama. He also uses many nods and hints towards other literature. This was extremely common in the ancient era, but Heliodorus could be very subtle and clever about it. In this sense he was kind of like the Vladimir Nabokov of the time.

My main source for this was the 2008 edition of Collected Ancient Greek Novels edited by B.P. Reardon. This includes translations of over a dozen full and partial novels, as well as nice commentaries on each. The book has a good foreword by J.R. Morgan and an introduction by B.P. Reardon.