In every episode of Charmed you see when they get the Book of Shadows out, the pages are clearly like four pasted together so they look thick...but every time they turn a page, you can clearly see that they are badly taped and just have nothing on them. I know it's not the biggest mistake...but at least I spotted something!
I looked in a book about Charmed and it was all behind the scenes, someone actually wrote and illustrated the ENTIRE Book of Shadows. What you saw was NOT a slip-up. Maybe you need to look closer or get glasses. Trust me, I'm a HUGE fan of Charmed.
Actually, you're wrong because I read an short article in a magazine about the Book of Shadow and it said that it is a very valuable, one of a kind, book. When they aren't using the book on the set, the keep it locked up in a vault.
Almost every page of the book is hand-painted and every spell they have used on the show has been added to the book. And just for a little more info about it, it weighs 9 pounds, 7 ounces!!! It's not fake! It's as real as you can get with something like that!!!
I saw a documentary on Charmed awhile ago now, there are actually a few copies of the Book of Shawdows, one that is rigged up for all of the special effects and another one that has blank pages in it so it can be added to, there are also a few others but i can't remember the rest......