The May/June issue of Writer’s Digest Magazine includes an article on “How To Build Suspense With Backstory,” by Romance writer Leigh Michaels. I liked this bit:

The suspense we’re discussing here doesn’t necessarily involve the characters being in peril; it’s created whenever there’s something the reader wants to know. Will Joe kiss Brenda? Will Sally give in to Brad’s demand that she work for him? Will Jared answer Katherine’s question or dodge it?

Whenever you cause readers to be curious about what comes next, you’re creating suspense. Suspense rises naturally from good writing—it’s not a spice to be added separately.