QBI: Queen's Bureau of Investigation — Ellery Queen

From cons to kidnapping to murder, eighteen ingenious stories showcase the talents of “the prince of American detective fiction” (Kirkus Reviews).
 
The agents of the FBI are fierce, brilliant, and brave -- but nothing in their files can compare to the puzzling mysteries that have been tackled by Ellery Queen. He is a one-man crime-fighting force, whose areas of expertise range from murder and blackmail to rare books and buried treasure. At the headquarters of the Queen's Bureau of Investigation, or QBI, there's no crime that can't be solved.
 
Whether investigating a trio of widows, a bumbling Shakespearean actor, or a blackmailed Sicilian, Queen is quick to deploy his secret weapon in the fight against crime: his brain. Each of these eighteen stories is an elegant puzzle, crafted with all the wit that has made Queen the most famous detective of his age.