I'm not much into mysteries, especially when the puzzle is the main draw and the characters play second fiddle. But when the mystery is part of what makes a character tick, that's compelling reading. I'm reminded of one of the players in The Usual Suspects (name withheld to protect those of you who haven't seen this brilliant film - place a hold here!) and how the secret of his identity is revealed only in the final scenes.
Often when a story is narrated by a child, the tension comes from what is called the 'unreliable' or 'naive' narrator. The child gets to tell the story, but doesn't know everything or even understand all that he sees. The trick for the reader then becomes to read between the lines, and infer the part of the story the narrator can't tell you.
Emma Donoghue uses this technique to good effect in Room, the story of a boy and his mother who have lived all of his short life confined in an 11 by 11 foot room. The reason for their captivity is only slowly revealed as 5 year old Jack gains the intellectual capacity to start asking questions.
Peter Carey creates a sense of tension in His Illegal Self by telling the story through a narrator alternately known as 'the boy', Che and Jay. Jay lived a comfortable life with his grandmother in an apartment overlooking Central Park; When he is spirited away by a woman he supposes to be his mother, Che lives in a van, or a trailer, or anywhere else they can find to lay down, somewhere in Australia.
Nine-year-old Lawrence struggles to recount the story of his road trip from England to Rome with his mother and pesky little sister in Matthew Kneale's When We Were Romans. But why did they leave home so abruptly? And why does his mother believe they are being followed by Lawrence's father? The bewildered Lawrence tries to make sense of the strange adult behavior around him but prefers to read about science and history - the only bits of information that seem true to him.
A narrator can also be unreliable because of a mental illness or a disorder. In Mark Haddon's The Curious Incident of the Dog in the Night-time, Christopher, an autistic 15-year-old, sets out to solve the mystery of the murder of a poodle who is found on a front lawn with a garden fork through it. Christopher admires Sherlock Holmes and sets out to prove his favorite detective's methods by using them in the investigation of the death. Christopher has amazing powers of focus, but can't see the social clues between people that might lead him to understand the incident.
In a recent Portland Literary Arts lecture, author Elizabeth Strout talked about how fiction provides one of the few ways to really understand what it's like to be someone else. Even when seeing through a character's eyes is like looking through a hole in a wall and trying to figure out what's on the other side, the mystery is worth exploring.