Graveyard of Memories by Barry Eisler

Graveyard is a prequel to the compelling John Rain series. John is a Japanese-American former soldier who becomes a world-renowned professional hitman. This book shows how that transformation happened. It's really kind of a sad book because circumstances beyond his control force John to do a lot of things he might not otherwise have done. And he laments the life he wishes he could have had.

If you're a fan of the series, this tome fills in some of the blanks. If you're new to the series, check out some of the earlier works such as Rain Fall and Hard Rain.