I haven't seen the movie, so I don't know how the two compare, but I enjoyed the book. The characters were very believable and I fell in love with four-year-old Grayer (AKA Grover.) Some people might feel parents couldn't be that self-absorbed and selfish, but I have seen the same things as a teacher. It is heartbreaking to see the results of families that have no time for their children - intentionally or not.
My favorite parts of the book were Nanny and Grover. Grover made me laugh out loud several times. He also made me cry several times as he tried to deal with his family. I related to nanny. She kept finding herself in difficult situations with her employees, but was unable to stand up for herself until the end of the book. Everyone in her life kept telling her to do so, but she would think of how it would impact her relationship with Grover and decide to let things slide. When the book ended, I cheered for Nanny and cried for Grover. Although Nanny spends the last minutes trying to convince the family to change, I don't think they will.
A note if you want to read this book - there is a lot of swearing and some sexual innuendos because the dad is having an affair with a woman he works with. It isn't explicit, but it may be offensive to some readers.