It's a hard task for a writer to maintain the forward motion of a novel. We want to keep the reader in suspense with our lightning-fast plotting and scene structures, but we also want the reader to have all of the information necessary to fully grasp the story. When information is given in a way that slows the plot and takes the reader out of the action, a “pause button violation” has occurred (PBV taken from Tim Wynne-Jones' website). He says, “Think of watching an episode of a TV series for the first time with an ardent fan who has control of the zapper and every time a character appears on the screen, your friend pushes the pause button and explains to you who this guy is.”
There are a lot of ways in which an author can commit a “pause button violation.” Many pause the action to inform the reader about a particular setting, an overly intricate and distracting description of a room or a landscape. Some writers pause to describe the way a character looks, pointing out each and every ultra-specific detail about their features or clothing. However, the largest “pause button violations” are committed through long passages of backstory. Lengthy backstory slows the plot, distracts the reader, and makes the viewpoint characters seem less authentic than they would be otherwise. Less backstory means a more believable narrative.
I'm currently trying to include large amounts of backstory in my own work without slowing the pace. As I said, it's a difficult task.
Just finished: Artemis Fowl by Eoin Colfer
Currently reading: Sapphique by Catherine Fisher
Up next: The Graveyard Book by Neil Gaiman