Based on the 1994 book "One for the Money," by Janet Evanovich. Evanovich has published 24 novels on the Stephanie Plum series. The 24th novel, Takedown Twenty, was published on 2013.
Janet Evanovich told USA Today that "Katherine Heigl is the perfect Stephanie Plum" and that nowadays whenever she writes about Stephanie Plum, she sees Heigl's face in her head.
Katherine Heigl's hair in the movie is actually a wig, as she wanted it to stay true to its description in the books and it would've been difficult to get her real hair to look like Stephanie's should.
The second lock picking scene where Stephanie picks a padlocked door is inaccurate. The tool she is using is a bypass knife not a pick. A bypass knife is used to exploit certain poorly manufactured locks, which does not include the BEST branded lock used in the movie. You can also see the tension wrench being held nowhere inside the lock tumbler in her right? hand. There is no way this lock would actually open with this manner of picking.
In addition to Stephanie referring to her cousin as "Sgt" Gazarra, we see him wearing both the single bar of the Lieutenant on his collar, and the double bars of a Capt. He obviously didn't get promoted, as we later see him wearing the Lt. bar again.