Today, I’m going to steal from three sites who explain Expository Lumps very well: Gary Corby’s A dead man fell from the sky…, cochisewriters, and everything2. After the line, there is nothing original of mine. Please visit the sites if you would like to learn more.
You know what the expository lump is, of course: that paragraph or page—or worse yet, pages—in which the author stops the story to tell you everything he knows about a particular character, setting, situation, etc. His intent is good—there are things the reader needs to know—but not all of them, not right now. And not all at once.
Expository Lumps are a (relatively) benign cancer which must be excised for the good of the book. One character goes on and on telling another character something they probably should already know. The real target is the reader, who certainly doesn’t know whatever is being explained. This is the author’s dodgy way of delivering information direct into the reader’s brain.
Expository Lump is a particular disease in science fiction. “As you know, Captain, the hyperdrive works by folding space into tiny packets of…” followed by two pages of exposition.
The expository lump has been identified as appearing in two distinct forms; the dialog lump and the narrative lump.
The dialog lump is perhaps the standard form in which the expository lump used to (and still does) appear in science fiction; otherwise known as the “As You Know, George, the Space Station’s Orbit Is Degrading Rapidly, and We’re Running out of Air” moment. In its classic form this where a character begins a sentence with the phrase “As you all know”, and then proceeds to spew out a lump of background information which everybody already knows, except of course the reader. Thus whilst it appears as if there are two characters having a conversation, it is really the case of the author having a one-sided conversation with the reader.
The narrative lump is where the reader is suddenly confronted with a page or two of text that appears to have been randomly inserted from an encyclopedia the author had conveniently to hand. … in which the author unloads a few hundred words of undiluted research upon the bewildered reader.
What both forms have in common is the desire by the author to suddenly deliver a “brutal overload of information” to the reader in order to establish the credibility of the unfolding tale.
Unfortunately, this lump… isn’t the exclusive province of the novice writer. We all risk writing it. As we get better, perhaps our lumps and dumps are shorter and a little less obvious: a sentence or two, rather than a paragraph or three.
New writers make two mistakes. First, they haven’t learned to trust the reader to figure things out. Second, they haven’t learned that the reader is their partner in creating the story, filling in what the writer leaves out. As a result, the new writer takes it upon himself to describe and explain everything.