Authors:

The thing about the books is that they really talked a lot about what was going on inside of Bond and the inner dialogue. It's very hard to project that onto a screen because Bond doesn't talk a lot about how he feels. But, when you have an actor like Daniel Craig, he's able to convey the inner turmoil and the conflicts. He's given Bond his humanity.

Source: collider.com
The thing about the books is that they really talked a lot about what was going on inside of Bond and the inner dialogue. It's very hard to project that onto a screen because Bond doesn't talk a lot about how he feels.