Cam Jansen

The Cam Jansen mystery series is a Children's Literature series by David A. Adler. Quoting from Wikipedia:
 * A series of books following the exploits of a fifth grade female detective named Jennifer "Cam" Jansen and her best friend Eric. Nicknamed Cam for her photographic memory, the protagonist closes her eyes and says "click" at various points in a story, mimicking the noise of a camera while memorizing a scene in front of her. She later recalls these scenes to aid in solving a mystery. The Cam Jansen character was based on an elementary school classmate of Adler's who was believed to have a photographic memory.