Avenger
by Frederick Forsyth (2003)

Ricky Colenso travels to Bosnia to volunteer as an aid worker. A few weeks later, he disappears and is never heard from again. A family grieves and is offered little hope–the killer has vanished.
Along comes Attorney Calvin Dexter (Avenger).
There is no doubt that this is well written. The prose flows easily and the author gets his characters and setting across vividly.
But there is so much back-story here it gets tiresome. Significant portions of the narrative are in the past. And each character, as they are introduced has their own background.
There is a story here, probably of novella length. But I got so fed up with all the background and lack of pacing I gave up after getting 2/3 of the way through.