Daniel Craig thinks his co-star Rooney Mara is "perfect."

Daniel and Rooney star in upcoming drama The Girl with the Dragon Tattoo.

Several actresses wanted to play Lisbeth Salander, including Natalie Portman and Scarlett Johansson.

Daniel is elated that producers decided to cast Rooney.

"There were shenanigans going on while she was being cast," Daniel told Time Out London.

"David Fincher was adamant [about Rooney] and I get that. Just look at the beginning of The Social Network, she's phenomenal. She's got something about her, but also she's physically perfect."

Daniel was impressed with Rooney's versatility. She embodied every facet of her character.

"When she puts the hoodie on and the leather jacket, she looks like a 14-year-old boy, she looks sexless. Which is perfect. The other side of it is that when she doesn't have that on, she's really sexy. That combination is absolutely true to the book," he said.

Daniel is astonished by the popularity of the books which inspired the movie. He is happy that the tomes written by Stieg Larsson have such a widespread readership.

"I stole a paperback off someone on holiday. Then I read the other two," Daniel recalled.

"You'd be at the airport and see the cross-section of people who were reading them, that's how I noticed them... You'd find 80-year-old men and 14-year-old girls reading it."

The Girl with the Dragon Tattoo will be released in the US on December 21.