When most writers are asked what moves a story forward, they answer, “The plot.” The story is an accumulation of events, dominoes that clink one after another until the last one falls. In order to facilitate this moving forward of the story, too many beginning writers fall into what I will call the ‘2d Trap’.
Imagine if you will, a side-scrolling video game. Most people think of Mario. In the classic game, each level is like a chapter. You start on one end and finish on the opposite. In the middle, your protagonist meets challenges and enemies that would stop him from reaching his goal. Perhaps the protagonist must also solve a puzzle. In the end, however, the moving forward is the goal. Complete enough levels and you reach the prize. Write enough chapters and you finish the book.
In these side-scrolling games,the action is all two dimensional. You can move either left or right. Depth does not exist in this flat world. This is the same with many books written by beginning writers. I would say my earlier manuscripts are plagued with the same shortcoming. They lack depth.
A book may have an excellent idea that it is built on, an intriguing ‘What if?’. It may also hit every one of Blake Snyder’s Beats from Save the Cat. The grammar can be fluid and the voice age appropriate. Everything can be written correctly, but if the characters are one-dimensional, the whole book will feel thin. 2D characters must not exist in a 3D world.
Characters must have range. They must not be perfect in the beginning, leaving no room for growth. They must have a past, or a compelling reason for a lack of past. People do not move linearly. We get stuck, move backwards, go on on side trails. Sometimes our motivations do not match up with our actions. We let ourselves and others down.