I think part of the reason this movie was made...and is aimed at us gamers who actually play all the Nancy Drew PC games. There's been a lot of movies lately based on video games, and I think this in one of them.
So this movie does not follow any book. But it does follow parts of the games. I buy and play every Nancy Drew games as soon as it comes out. And the games are from HerInteractive and are for "girls who aren't afraid of a mouse!" And some of these games actually won Parents' Choice Gold Awards. They are not only fun but you can actually learn a thing or two while playing.
I took two of my step children with me to go see it and they loved it! The 10 yr. old had started playing her first Nancy Drew game a day before I took her to see the movie, and she was having so much fun playing the game I thought she would enjoy the movie as well. And I was right...she not only loved this movie but couldn't wait to get home to finish her first game and start another one.
My other step daughter is only 7 and she also loved the movie but she is still a little to young too play the games yet, but she enjoys watching her sister play at times just to see what's going on.
The games are based for children 10 yrs and older. All the games usually get pretty descent reviews and are classified as adventure games. For more information on the games just check out HerInterative Nancy Drew games. So personally I thought the movie was pretty good and I will buy it when it comes out on DVD.