If DVDs can have extras, so can books. Except these are free and you don't have to pay loads more for a special edition. And you won't even need to invest in blu-ray.
If it's trailers that you want, we've got them, along with the background story as to how they came about.
If it's an author's commentary you want, we've got links to more articles about how the book came to be written and published than you can shake a stick at. Should you have a stick handy.