Idle Playgrounds by Sheralyn Pratt

Rhea Jensen is determined to put her career as a private investigator behind her, but her best friend, reporter Kathryn "Kay" McCoy, is just as determined to keep Rhea in the detective business. Rhea ends up on the trail of a mysterious group of daredevils, a case which makes her the target of an age-old secret society. Rhea's gutsiness is matched by her vulnerability; her confidence and brilliance when it comes to her work contrasts with her confusion and self-doubt when it comes to personal relationships. Mystery, action, romance--this book is great fun.