I heard Harlan Coben talking about it on NPR and it sounded like the two of them had a ball from start to finish. First she called him and he was tickled to get a call from her, though he hadn't met her.I've just looked this up and it does look like a good read. Pleased to see that Reese Witherspoon does the audio version. If I do catch it - it will almost certainly be over audio.
She had an idea for a novel and he thought it was a fine one. So he wrote it, but used her plot idea and called her almost every day to get her thoughts about the main character.