Treat backstory like a pungent spice. I say this to encourage you to picture a jalapeno pepper that can set your mouth on fire, every time you even think about adding backstory into your book. What you need is subtlety.
~ Sandy Vaile
Backstory is like a flavour you can’t quite pick, lurking in the layers of a curry. You know it’s there and it enhances the flavour, but it’s intangible and fleeting. Use it sparingly!
Delayed gratification hints that something terrible is going to happen, and then delays the resolution. It’s that interval between the promise of something awful and it actually happening, where suspense resides.
Suspense doesn’t always have to be about physical danger. Making the reader worry is a universal concept that can be applied to any story.