Hitchcock said he seldom made mysteries—maybe just once. He made movies that relied on suspense. I remember Elmore Leonard, in an interview, saying something similar. Everyone called him a writer of mysteries. He said he'd never written a mystery. He wrote suspense. Of course both Hitchcock and Leonard were artists, great stylists, but they both used suspense to keep their audiences (watchers and readers) engaged.
A mystery is a puzzle, an intellectual experience. The reader is given given clues and puts the clues together and solves the puzzle. The key is that the characters, at least some of them, know more than the watcher or the reader. If you have a detective, the reader or watcher, solves the mystery with the detective. Suspense is more of an emotional ride. In suspense the watcher or the reader knows more than the characters. If you're writing multiple POV's this is easier to pull off. I notice Leonard often uses multiple POVs. You give the reader more information and then you create suspense by putting characters in situations. For example, Sal is going to murder his wife because she's cheating on him. We know he's going to do it in the bedroom when she's asleep. The reader has to watch her stay up late watching a movie, has to watch her take a sleeping pill etc...We're unsure Sal will go through with it...You get the idea. You could make all kinds of things happen to cause more suspense etc...but the main idea is this simple: you use the information you give the reader to create suspense.
Hitchcock explains why having a bomb go off under a table, surprising the audience, is the wrong move. To create emotional suspense, to get the audience working for you, you need to let the audience know there's a bomb about to go off under the table. Then have five people sit there and have a conversation about what they did last night. That's suspense. I'd add, the audience will care because people are empathetic (with a few exceptions) even if they don't know the characters. Check out the video below to hear this idea in Hitchcock's own words.