Reddit reviews The Complete X-Files: Revised and Updated Edition

I think The Complete X-Files: Behind the Scenes, the Myths and the Movies is a book which covers this sort of stuff. I haven't read it yet, because I am waiting for the Revised and Updated Edition which includes Season 10 to come out in November.

There is also The X-Files Official Collection, which is content from the official X-Files magazine, which was released while the original series ran, collected into three volumes:

• Volume 1: The Agents, the Bureau and the Syndicate
  
• Volume 2: Little Green Men: Monsters and Villains
  
• Volume 3: Conspiracy Theory - The Truth, the Secrets and the Lies

https://www.amazon.com/Complete-X-Files-Revised-Updated/dp/1608878457/ref=sr_1_14?ie=UTF8&qid=1478955379&sr=8-14&keywords=the+x+files