The trilogy as an art form has been around since the Ancient Greeks performed three interconnected plays during festivals to honor Dionysus, the god of wine and festivity. Trilogies in books stem from those original plays. The same author will write three novels with connected characters, themes and storylines from one book to the next. Trilogy novels are very popular due to the fact that readers get incredibly involved with the characters and want to absorb the next installment as soon as possible.
One of the most popular examples is The Lord of the Rings Trilogy by J.R.R. Tolkein. The author originally intended it to be one novel published in six parts, but was made into three books. The trilogy follows the travels of Frodo, a peaceful hobbit, as he attempts to defeat an almost endless stream of evil at every turn with the assistance of many different allies. The novels have been popular since they were published in 1954, but the hugely successful movie trilogy has added to their already loyal fan base.
Stieg Larsen is the author of The Millenium Series, in which the main characters are Lisbeth Salander and Mikael Blomkvist. These novels follow the two main characters as they find themselves in many precarious situations that typically involve powerful people using their wealth and power to commit unspeakable acts.
The Fifty Shades Trilogy, penned by E.L. James, follows the sexual journey of a young woman through college and into parenthood with a man she meets by accident. This was James first attempt at fiction writing and the trilogy became wildly successful in a short amount of time.
Suzanne Collins had an unexpected hit with her The Hunger Games Trilogy, a story that takes place in a dystopian future where the dividing lines between classes can mean the difference between life and death. The heroine, Katniss, becomes a figurehead for rebellion to the lower class and eventually elicits the change she tried to create.
The popularity of the trilogy form of novel writing will not fade. It gives the avid reader a collection to look forward to and the publisher is guaranteed to reap a sales benefit. For those not interested in reading the trilogies, the movie renditions of such novels are often playing on Direct TV.