Here you'll meet Harry Dresden, professional wizard, Chicago resident, and police consultant.
This book is the start of a great (if violent) series, and introduces you some of the regulars like Lt. Murphy (Chicago PD,) Susan Rodriguez, (tabloid reporter,) "Gentleman" Johnny Marcone (Crime lord,) Morgan (magical enforcer,) and my favorite, Bob the skull. (Bob's a pervert. And funny.)
Fair warning, this book (and the series in general) has a lot of blood, gore, cussing, and sex. I wouldn't recommend it for younger audiences. Or teenagers for that matter.