Books can fullfill an active imagination with stimulating our ability to put ourselves in any situation.
Of course a film can do that, but a film is easy, it is for those who want to be lazy. We hardly need any thought at all.
The images are put before us, the dialogue and even the way the film will finish.
A book also has a specific story, dialogue and outcome, but we make it real. We make the images in our heads...no...we conceive the images in our heads.
A book is not better than a film, and vice versa, but its like sex; What mood are you in today? sensual or kinky, lazy or thoughtful?