Actually I'm not sure I agree with her decision to read the book. If the script went in a substantially different direction, then her initial reasoning was sound: she should base her performance only on the script's version of the character and not confuse things by considering an alternate slant. (Just as actors playing a character that's previously been played by someone else often choose not to watch the earlier performances, wishing to create their own distinct characterization rather than just imitating someone else.) A book is the creation of one person, but a film is the work of many. Her director might have a vision for his version of Nikki Heat that's substantially different from what's in the book, so if she draws too much on the book, it might clash with what the director wants from her.
Don't you think, though, that that same logic would NEGATE going to the "original person" of the character to get tips?
Hmm, maybe. I hadn't thought of that. But the idea here was that the Natalie character was very "Method," feeling she had to experience the reality of a role in order to get into character. The reality is Beckett; the book's Nikki Heat is Castle's interpretation of her. The screenwriter's Nikki Heat is a different interpretation (although an interpretation of Castle's interpretation). So I can understand her wanting to experience the reality yet not be distracted by an additional fictional interpretation. Drawing on too many sources of inspiration could hamstring an actress, limit her ability to bring something fresh to a role.
But maybe you're right. Maybe her insistence on "Method" here, on learning to mimic the real Beckett, is a bad idea. After all, Heat isn't Beckett. She's presumably a more sensationalized, glamourized, sexualized version of Beckett. (I haven't read the book yet. Keep meaning to get it from the library.)
Hey, come to think of it, how the heck did Castle get hold of this actress's audition tape for the movie? Who in Hollywood bothers to keep the writer in the loop? Although I guess he's a big enough name that he could've gotten an Executive Consultant role or something.