The Bubble Gum Thief.
(Books)

Special Agent Dagny Gray is smart, athletic, and fearless. She's also fragile, depressed, and anorexic. If she doesn't get healthy soon, the FBI will drop he-and she'll never have a chance to end the crime spree of the so-called "bubble gum thief." It all started with the theft of a pack of gum, and the ominous note he left behind: THIS IS MY FIRST CRIME. MY NEXT WILL BE BIGGER. Every two weeks, he delivers on this pledge, committing a bigger crime, and promising that the next will be even worse. When petty theft gives way to bloody murder, the stakes become clear. He may have begun with the smallest crime possible, but he's building toward the biggest crime imaginable.