Tension in a book can, literally, have you perched on the edge of your seat. Will they, won't they? Will they get there in time? Will the secret be revealed? I've had to put novels down in the past to have a rest from the onslaught of that story's tension.
Elizabeth Spann Craig has written a wonderful article on just this, Tension & Pacing in Your Fiction. It's well worth a read. Have a look.