The Bookseller by Mark Pryor

Hugo Marston isn't your traditional investigator - he's not a cop, he's the chief of security for the US Embassy in Paris. But somehow, he just can't keep to himself when he sees wrong being done.

Here, the wrong is the abduction of a Paris bookseller, a man Hugo counts as a friend. The fact that everyone else on the street lied to police and said that Max went willingly means only Hugo is really investigating. Good thing he's on "vacation" this week.

I recently read the second in this series (The Crypt Thief) and enjoyed it enough I hunted down this first in the series, too. Unlike that book, in The Bookseller the reader doesn't know any more than Hugo does - we're piecing together the puzzle as he is.