Book vs movie: One for the Money ISN'T Worth the Money!

Ouch. I had pretty low expectations for One for the Money but as low as they were, they weren't quite met.
And I'm not sure why.  I enjoyed the book, it was a fast, funny and fun read. I enjoyed seeing the divorced and newly unemployed Stephanie Plum rise to the occasion when it came to getting her man. I enjoyed seeing her get the best of Morelli, and I enjoyed the fact that at the end of the day, he came, in a way 'crawling back.' Besides all that, there was the threat of Benito Ramirez; the book was full of excitement and suspense.
And I was looking forward to the movie. I thought it would be just as much fun.

But the film just fell flat for me.  Heigl looked fine as Stephanie Plum, except for some awful skin that an equally awful makeup artist and cinematographer did nothing to disguise. But she did little beyond a half-hearted attempt at a New Jersey accent - the credits include two dialect coaches, no less - to conjure up a real person out of Janet Evanovich's very popular fictional character. Instead of being royally pissed and feeling justified about bringing Morelli in, Heigl's Stephanie vacillated between cutesy flirtation and vapid exasperation.  Jason O'Mara's Morelli, on the other hand, was surprisingly good. And real. It was like he and Heigl were in two different movies. 
Evanovich's truly terrifying Benito Ramirez character was chopped to nothing; such a shame to do that,  not only to the actor, Gavin Keith-Umeh, but also to the storyline. There was so little left in the way of threats and obstacles, it was almost laughable.

What happened?  Why was the pacing so off? Where was the chemistry? Who filled the story with such stilly over the top dialogue?
The director, Julie Ann Robinson has done mostly episodic television including a half dozen episodes of Greys Anatomy. That presumably is how she and Katherine came to know each other; she could have served that friendship better by pushing Heigl more, getting to the truth and thus the very real humor in the situation.
The trouble may have begun though, with the writing; it usually does, right? Given the source material is well done - (while it's not Shakespeare, milions of Evanovich's fans would say the book is both funny and well done) it may indeed be the trio of female writers that started it all. Lix Brixius has been nominated for her work on Nurse Jackie. A talent she sure didn't bring to this project. This is Karen Ray's first screenplay, period. And Stacy Sherman is best known for a documentary she co-wrote.
Ladies, including Heigl who is credited as a producer, you should all be ashamed of yourselves!
While most of the characters are weak and stereotypical, the female characters in particular are more caricature than character.
Heigl is left to flail around foolishly. With the exception of learning to shoot by the end of the movie, she barely seems to grow. Even Sherry Shepherd's character has a bigger arc - as Lula the hooker, she gets to move off the streets and into Cousin Vinnie's office as staff!  Ana Reeder as Connie is the wisecracking secretary. Debbie Reynold's the crazy, loud-mouthed grandma. Debra Monk the mother frantically trying to get her daughter paired up. I can just picture them watching the dailies and thinking it was all so hysterical when in reality it is all just so dreary.
Honestly, I can't be bothered to try to analyze this any more thoroughly; it just doesn't seem worth the effort.
One for the Money aka None for the Money aka Not Worth the Money aka Save Your Money. You get the picture.