Yes, they can add dimension to the story by adding depth to your characters or suspense to the plot--it's a great way to bring in history, further sympathy for your MC, etc. If done well, flashbacks put me in the moment, experiencing the past first hand. And often times, it's better than trying to tell that portion of the story later through exposition or discussion.
As a reader, I usually hate when I see a flashback coming. I don't like the current action to be interrupted. Sometimes, I even speed read past the flashback and jump right back into the story because heh, time is precious and I know it's just a sob story about the last time the MC saw his mother or was in a car accident that killed his whole family. *snicker*
If that's the case, the author isn't doing their job.
One thing that can make or break a flashback is the transition. If the transition is choppy, or cliche, I'm out. The way to make this work is by making the transition natural. Having a flashback triggered by a smell or an object--or even a person usually works. But won't if you don't have this next thing:
If I'm not hooked, why should I care about the MC's past? If I am, I want to know what's hurting them and what makes them tick.
Now, I'm no flashback guru, but I wanted to share an excerpt of how to maybe get away with a small memory without having to dive into a full blown flashback. This was originally part of the first draft of my last novel. It's not in the story anymore, but I think this is a good example of how to have a smooth transition and say a lot in just a few words:
“This you?” he asked, inclining his head to the far wall.
I knew he was referring to the collage of pictures Mom had pasted of me everywhere. She could never take any down and kept placing one on top of the other.
My hope of ignoring the wall so it would distract him from doing so, was in vain. He was across the room before I could even finish my thought. I silently cursed Mom for not ever taking down "the awkward years." It was no big deal with just the two of us, but knowing that this guy—however strange he may be—was going to get a close look at my blemished face complete with braces, made me nauseated.
I cringed as he studied the photos. Memories of me in third grade flashed to my mind—pigtails and all. When the recess bell rang, I remembered skipping to the flagpole to meet Bobby Hendricks. He had passed me a note saying for me to meet him there because he thought I was cute. He said he wanted to kiss me, but I first had to tell him my deepest, darkest secret. Of course wanting to be on the receiving end of such a kiss, I told him that I had invisible people who lived in my backyard.
I remembered the way his eyes turned cold and dark. He laughed in my face and told me I was a freak. Instead of a kiss, I found myself face-planted onto the concrete. Tennis shoes and sandals stomped around me. They teased me and called me the name that has haunted me ever since. "Crazy …
“Hhm?” I said immediately, snapping my head up to his.
What about you? Flashbacks: Yea? Or Nay? Do you prefer them in italics as opposed to plain text? Do you use them in your writing? Is there an author that you think is the flashback guru?
Red. Head. Out. :D