When reading a passage in a book, readers need some sort of framing to give them context as to what is being said. In art, the common word used is structure. To show what I mean, here's a picture I painstakingly drew:

If I told you that this represented something, you'd be hard pressed to figure out what it was.

Here's another picture that took me many hours to come up with:

What is it? You don't have to look real hard to figure out it's a tree. The only difference between the first picture and second is structure.

Writing stories require structure. It's the foundation of good storytelling.

My writers group is taking a small hiatus due to the holidays, so to get my kicks I've been going to another writing group. I know. Drugs would be more fun, but I tend to react pretty badly.

After getting settled at a conference table, a woman took out pages from her fantasy and read, laying down a lot of backstory. Sometimes backstory helps to explain the motivation of a character. But too much of it can slow down the pacing, overwhelm the reader by asking them to remember too much, or make it feel like nothing is going on because no one's really at risk. I mean, the events have already happened.

What if the backstory is essential to the current storyline? And what if there's a lot of it?

The basic strategy is to just give enough backstory when the storyline needs it. Otherwise, writing more of the backstory isn't going to do any good because the reader will not likely remember it. Backstories for fantasies tend to be long and complicated because they deal with fantastical characters and histories. So that's a lot of unconventional names and events that the reader has to memorize.

One thing my fellow writer wasn't doing was structuring her scene. There's a beginning, middle and end, but that's not what I'm talking about. One of my first books on writing was from Dwight V. Swain, Techniques of a Selling Writer, where he talked about MRU's: motivation reaction units.

A man slaps a woman. She gets pissed off. She wants revenge. Then she kicks his nuts hard.

The motivation is the slap. From there, her reaction is anger and wanting revenge, which are feelings and thoughts. And then action is needed, her kicking his nuts in. This in turn can be the man’s motivation, which leads to his own reactions, followed by action. I do want to point out that action could be dialogue because not every book in the world is going to involve nut-kicking.

Backstory can be placed within the thoughts, the reaction part. This helps structure our understanding. So when the woman gets slapped, her initial shock is something that should be shown. Then we can go into her backstory of being slapped by the love of her life, which was the start of her worsening abuse. Having learned from that experience, she promised herself that she'd fight back whenever a man abuses her, and wham, foot flattening the nads.

This is not the best example, but it gives you an idea of where to place backstory. Still, everything is now contextualized. We see the slap, her shock feels natural to us because we'd be shocked as well, and her backstory fits into this context, so we don't question her resulting action, but cheer her on. We're rooted to her now, and that's important in keeping the reader interested.