Show don’t Tell, or so the old writing adage goes.
So much so that I either read or written the line above at least once in the last year.
It is one of the reasons why most of your world building never sees the light of day, otherwise it would get in the way of the story. However, there is a way to liven up all that material, fictionalization. Short stories, flash fiction, vignettes, asides can all be used to give readers a behind the scenes look at the story. But doesn’t this get in the way of the story itself? It can. Like a prologue it may lead the reader to wonder why are you not telling this story instead of the one in the book.
Enter the Internet.
Now, this phenomenon is nothing new. Entire franchises are built on the stories hinted at but never told in the “main” story line and many authors have compiled short story collections that tell concentrate on secondary characters (unless they get their own book which can also happen). With the Internet you can put these stories on blogs, on line magazines and websites as freebies to your audience. You keep them hooked by giving them more of what they want, you put all that world building to use and keep the story going.
A common method for modern and sci-fi stories is the fictionalized news story, maybe an interview with a character, or a series of news reports. The newspapers articles or TV reports serve as a perfect framing device for all that exposition that would otherwise slow down the pace in your book and it is in a format where exposition is not only accepted but expected. Other formats exists such as in-universe history books or school books. As always, consistency is the key (although it can be played with in-universe), the supplemental material has to support the main storyline/universe not distract, contradict or derail what is already established.
It is also a great way to keep a universe alive without exhausting the main story or maybe even a source for new stories and characters.