How is the start of The Lovely Bones tense?

The Lovely Bones does a great job of building tension in its first chapter. Susie's second line of narration, the second line in the entire book, says "I was fourteen when I was murdered on December 6, 1973." We immediately know from this statement that we are building up to something terrible.
The setting is also a major player in creating tension. Susie is walking home, alone, through a cornfield in the dark. At first, she is scared when she comes upon Mr. Harvey, but because she is interested in how he built his "hiding place," she agrees to go with him to check it out. By this point, we as readers (who have already been told that Susie is going to be murdered) have better judgment than Susie does, and can sense that going with Mr. Harvey is bad idea. Essentially, the beginning of the book is tense because of dramatic irony—the reader knows an essential piece of information that a character does not. Tension builds as Mr. Harvey begins to ask Susie stranger questions, until she, too, knows that she should be scared.