Improving on fiction

I ran across this synopsis of a thriller by a writer named David Bowker. I've never read him and I make no comment on his writing; I'm only using this synopsis as an artifact. Thus:

Mark is a mild-mannered twenty-three-year-old bookseller who makes endless lists about stupid things. His life changes when he reestablishes contact with his old girlfriend, Caro. At seventeen, Caro was an implausibly sexy, promiscuous, druggy big-mouth. Six years later, she's exactly the same and Mark falls in love with her all over again. Caro, who has nothing but contempt for Mark's lists and his choirboy attitude, asks him to prove his love by giving him a list of her own: a list of people she wants him to kill for her. As things begin to spiral out of control and the bodies pile up, Mark himself becomes a target and realizes that to survive, he needs to be as ruthless and decisive as his enemy.

Sigh. It sounded all right until the part about being "ruthless and decisive;" it makes it sound so movie-thriller-ready. And I wanted it so badly to be a comedy:

Mark is a mild-mannered twenty-three-year-old bookseller who makes endless lists about stupid things. His life changes when he reestablishes contact with his old girlfriend, Caro. At seventeen, Caro was an implausibly sexy, promiscuous, druggy big-mouth. Six years later, she's exactly the same and Mark falls in love with her all over again. Caro, who has nothing but contempt for Mark's lists and his choirboy attitude, asks him to prove his love by giving him a list of her own: a list of people she wants him to kill for her. He would like to agree, but since he's only 23 and can't even make a decision on what kind of beer he likes, tells her he doesn't feel quite ready to become a dashing assassin. But he offers her a compromise: he'll take the first step and go and buy a gun with her if she'll go to counseling for what is obviously a persecution complex and a lot of misplaced hostility. After she leaves, he calls the FBI, and when he shares her hit list with the young, hot FBI agents (to be played in the film by 30-something cast members from recently cancelled NBC series), they realize all the people on the list are in the witness protection program. Therefore Caro must be an agent for a ruthlessly inefficient (or she wouldn't have approached this lunkhead) international criminal conspiracy. Thus begins a comic story of double-cross and triple-cross, as the FBI tries to get Mark to get Caro to lead them to the mastermind of the whole operation who, of course, has his secret headquarters in an empty warehouse somewhere in the Port of Long Beach.

The story ends with all the shootouts of the over-serious original idea, but it's funnier.