I know I might be in a minority, but I enjoy watching films with the director's commentary. I like hearing how the movie was put together, how choices were made. Knowing that Indiana Jones initially planned an elaborate sword-fight that got scrapped because Harrison Ford had a cold and realized it made more sense for his character to shoot his attacker. Or that the famous "It's game over" speech in Alien was improvised on set by Bill Paxton. Or that Joss Whedon initially planned to have the Hulk "sniff" out Loki's true self among illusionary duplicates in Avengers. It's why Bruce Banner makes several references to being able to "smell the crazy" on Loki. But it was decided that the scene would play better if Loki didn't bother to take the Hulk seriously.
I like knowing the behind the scenes of decisions behind writing. When I met Roxanne St. Claire several years ago, she explained how she began writing the Barefoot Bay series as a request from her editor to do a small town contemporary romance series. At the RWA National Conference, I heard Sherry Thomas talk about how she began writing to get out of post-partum depression.
With Revelations, I decided to do a chapter by chapter commentary, sharing references, such as a request from a family with a handicapped child to include that child in the story. Where I didn't have time to fit in research details, I've included them in the commentary. I explain where I found inspiration and share credit for ideas which came from friends and family. I enjoyed sharing it and did it again with Metamorphosis. You can find them both by clicking on the book's page and finding the mirror.
I'm looking forward to doing it yet again for Inquisition. I go through each chapter and write a few paragraphs for each one. It's a fun way to look back on how far the story has developed and where it began. And it's a way to say goodbye before launching into new stories and worlds.