This film is an adaptation of the novels The Secret Dreamworld of a Shopaholic (Confessions of a Shopaholic in US and Canada) and Shopaholic Abroad (Shopaholic takes Manhattan in US and Canada) by British author Sophie Kinsella, using the novel's American title Confessions of a Shopaholic. The movie will definitely be different than the book series so if you love the novels don't go to the movie expecting it to be amazing like the books. The movie is based in New York instead of London with pretty much all of an American cast. I have also heard that the movie is the first and second book combined.
This is what it is being describes as:
A college grad named Rebecca Bloomwood (Isla Fisher) moves to Manhattan to nurture her shopping addiction and get involved in the New York magazine world. Though she is up to her neck in debt, Rebecca becomes a financial advice columnist and even manages to fall for a wealthy entrepreneur.
With the geographical difference I hope the movie doesn't ruin the essence of the novels series. It just seems it would be too much of a difference. I definetly didn't see Isla Fisher as Rebecca, but I like that they casted Krysten Ritter as Suze. Make your own decisions and see the movie if you want to.