There are various techniques for building tension in a story: the use of foreboding, the ominous comments of hindsight, the race against time or the ticking clock set-up, the sudden reversal of fortune or the shock revelation that trips up the reader and changes what we understand of the narrative. Writing in the present tense can also contribute to the breathless, fast-paced feel of a thriller. With this technique there is neither foresight nor hindsight. We do not have the bigger picture, only the frame by frame, chapter by chapter account. Like the protagonist we are in the moment. It’s a very modern style, well, I assume it is (people who know about the history of literature please correct me if I’m wrong).
I’ve written novels in the present tense and others in the past. Sometimes I’ve found that changing to the present tense gives a better edge to a story. In my latest book, Blink