Suspense fiction books are a hit nowadays because they contain elements no other type of book does. The type of bitter-sweet entertainment they present is that of a mystified entrapment that embeds itself in your brain. Progressively tightening it's grip on your mind until you're at it's mercy. They take you to an environment you're not sure you want to enter, but still extraordinary enough to delve into.
Suspense fiction books are so much better than other pedigree genres, such as whimsical fantasies, and stories about romance. They suck you in so much until it feels like you aren't just simply some bookworm hiding behind a novel, but a major player in the novel, actually giving the illusion that the hazards at hand to the hero of the story are yours to fight.