Fire Lover:  a True Story by Joseph Wambaugh

John Orr, growing up in Los Angeles, watched with awe the work of firefighters. Wanting to emulate his heroes, he became a fireman. Eventually, he became a fire captain and one of Southern California's most renown serial arson investigators, successfully apprehending a string of petty arsonists. But there was one Orr couldn't seem to track down, although the culprit used a simple device every time, and killed four people. When the fire lover made a mistake and left a fingerprint behind, investigators were stunned to discover that it belonged to none other than investigator John Orr!