Question: I got a letter back from an agent with a scrawled note saying, "not enough suspense." I write literary fiction, not mysteries!
Answer: The fact that she took the time to try to tell you something, should also tell you that she sees something good in your work. Yeah, I know close only counts in horseshoes, but still it's encouraging at a time when the mass market paper publishers are choosing fewer and fewer titles to send to press. So think about that, too.
Having said that, all fiction, in fact all tale-tellling, has an element of suspense, of "What happens next?"
To a fiction writer suspense means keeping readers guessing what will happen next. The term suspense, denotes how involved the reader is in your plot. If he or she already knows what is going to happen, there isn't any suspense (critics call it "predictable"), and little reason to continue reading. Hooks help increase suspense. I know most literary writers think they are above such things, but literary hooks are just more subtle, that's all.
"I inherited my brother's life," is a hook from a writer of popular mystery novels.
"It was the best of times, it was the worst of times," is a hook you may recognize from a literary writer of note.
To avoid predictable plots, make a list of 10 things that might happen next and pick the least likely. Or brainstorm with friends to come up with suggestions for unusual and exciting twists. Remember, keep your readers guessing.