I'm no expert about writing (yet). But I know what I like when I'm reading. And when I'm reading a thriller, I want thrills. I want to be forced to turn the page to find out what happens next.
Compare and contrast two recent reads, both thrillers set in Washington, D.C. What did one have that made me remark that it had 'a tight plot with page-turning suspense' and the other (which I have yet to finish) feel like it's almost a chore to keep plowing through? Both stories involve conspiracies that the protagonist has to unravel. Yet one was riveting and the other feels limp. As I said, I'm no expert, but one thing that seems to be missing from the second book is the almighty ticking clock.
In the first book, the ticking clock is the revelation that a terrorist attack is imminent. At first the protagonist and the reader are in the dark about the who, what, where, when and why. We just know it is very bad and it is coming soon. As the mystery is unraveled, the threat becomes more dire and the timetable shorter and shorter. The clock is ticking.
In the second book, there is no ticking clock (at least not in the first half of the story). And there is no imminent threat. There is an assassination attempt on the President in the first chapter. But after that there is only mystery. We already know the what, where and when. We are even given a purported who and why. We are now supposed to care that the who and the why are probably red herrings and a larger conspiracy is at work. But why should we? I'm halfway through the story and all we have are vague threats and inconclusive clues. There is no ticking clock or burning fuse evident. The danger is past. The thrill is gone. It remains to be seen if the suspense and action will ramp up in the second half.
I see now that the thriller I am working on needs a ticking clock. It has a bang up opening, like the second story above. But all it has after that (so far) is a mystery (like the second story). I know there is an imminent threat. I need to make sure the reader sees it and feels it, too. It does not have to be revealed all at once, there needs to be suspense. But in order to have suspense, they need to see the bomb under the table or the killer lurking in the shadows. They need to be thrilled. Otherwise, I'm writing a mystery and not a thriller.