My friend Jason worked through some interesting theories about the Book of Destiny and how it works.
He was nice enough to let me post them here (with my thoughts noted):
The Mercury Book
Some facts, observations, and theories …
FACT: The book contains all the story of humanity from the beginning to the end of time, such that a person can open up the book and read the past, read the present and read the future.
FACT: The book as drawn cannot possibly fit that much story in it literally.
THEORY: The book is partly telepathic, so that a person can open it to what they want to start reading about (say, five years into their own future), and they can find it somewhat easily. The book almost acts like an electronic document, with the human mind opening up different menu tabs: Doing a “Search” for a specific person or era.
FACT: It is somewhat overwhelming when someone first opens the book and tries to do this, as shown when Toby first opens the book and tries to find what happened to Leanna Creel on the night of her murder. But he does eventually find it.
FACT: It is possible for someone to cross out what is written in the book and write something else, and reality will change based on what has been newly written.
THEORY: The book’s telepathy must have to come into play for this to work as well. When Kid Thunder crosses out Drue’s name in order to make him cease to exist, that wouldn’t literally work … crossing out a character’s name just one time in a book doesn’t remove that character from the story. And yet …
FACT: … when Kid Thunder crossed out the name, Deliverance Drue exploded.
THEORY: The book can read intent. (“Delete all instances of Deliverance Drue from this point onward.”)
Me: Yes, this became problematic for me on the read through. A strikethrough shouldn't result in a man exploding to death. It might also have something to do with your suggestion that Kid Thunder is illiterate. Back in the west, people could just do an "x" to signify their name. The small amounts of writing they could do represented so much more. Maybe there's some of that in play?
That would fit right in. Yeah, it's interesting to wonder how much
specificity is required in the writing of the people who make changes.
When Sentinel wanted super-powered allies, did he have to specify, "An
archer named Shaft, a rocky giant teenager called Badrock, a purple
gymnast called Vogue ..."? Or did he say that Sentinel eventually
founded a team of superheroes called "Youngblood," and the book
improvised from there?
OBSERVATION: We are never shown anyone changing the past when acquiring the book. Instead they rewrite the present and/or future. However …
THEORY: … in theory, changes to the present would most likely change the past too. We were told that Sentinel wanted to have a team, and so he wrote in the creation of Youngblood. That means that Youngblood members would have to have been born, grown up into the kind of people who would become superheroes and then eventually join the Youngblood team that Sentinel writes into existence. He writes Youngblood into the present, but this would have to cause the book to revise the past to accommodate that. And of course it would have to revise the future as well to accommodate the change. Otherwise things would snap back right away and Youngblood would cease to exist one second after they popped into existence. Again, not something a real book can do, but one can picture it more easily if one thinks of electronic documents, which can change formatting of an entire section of a document based on a single deletion or addition.
At one point, Toby says that the entire world “changed and darkened” because Sentinel wanted to live in a world that was more intense, violent and extreme. For that to happen in the present, the book would have to reach back in time and recreate the socio-economic realities of the last couple decades (at the least) in order to create a present with more violent crime, etc.
Me: Yes, this one struck me as odd when we started talking about it. Why can't you change the past? It seems like some of the past is automatically getting changed, anyway. I think it's the one rule Moore set up, that you cannot change your own past, because then things would get too out of control.
I imagine that there are feelings that wash over a person upon even opening the book, and further feelings, instincts, emotions, etc. upon trying to rewrite it. I liken it to telepathy as far as comic-book terminology, but it could be something more primal than that. It might be that someone is simply overwhelmed by primal terror if it even occurs to them to try to rewrite their own past. Something akin to the self-preservation instinct. (What if I write something wrong and cause myself to cease to exist?)
WILDER THEORY: Revisions in the Mercury Book are what cause the “Reality Revisions” that create new Supremes. The timeline for when Leanna Creel stole the Mercury Book matches up to when Supreme 41 took place. Perhaps Leanna decided the world was too “extreme” so she slightly rewrote it when she reacquired the book, resulting in the Alan Moore revision of the Liefeldverse. As noted above, a revision of the present of necessity has to reach into the past. This is why the old Supremes tell the Moore version of Supreme that he is just popping into existence now, in 1996, but his memories and his history stretch back to the 1920s. Any change to the book has to ripple both backwards and forwards into earlier pages and later pages. (i.e., for the world to suddenly become a less violent place as of 1996 per someone’s revision, the book has to – to be simplistic about it – reach back in time and change things so that less people grow up in poverty and turn to lives of crime, etc. In other words, just changing one single sentence in middle of the book could conceivably require a full-scale “reality revision” i.e. the book rewriting itself starting decades earlier, and also into the far future as well.
FACT: Every character who has attempted to use the Mercury Book to change life in their favor has succeeded at first, but ultimately lost the book.
OBSERVATION: Theoretically that shouldn’t be possible, because a person should be able to read their own future, see the moment at which they lose the book, and rewrite that moment so it doesn’t happen. If that causes reality to change so that they instead lose the book five years later … well, again, they should be able to read five years forward, see it about to happen again, and rewrite it again. And so on to infinity. But this doesn’t happen. Which suggests …
THEORY: …. The Book does not allow that to happen. It’s built in that no one person can control or hold the book forever, so the book is able to selectively blind people to the future. As noted above, if the book has the telepathic ability to let a person see exactly the parts of reality they want to see, then the book could also possess the ability to block certain moments in time. It might even be able to exert a telepathic influence on readers, such that it doesn’t even occur to them to look for certain moments, or to rewrite certain things. This could be why it never occurs to anyone to try to rewrite the past, but instead only to start rewriting from the present forward. Or why sometimes it doesn’t occur to someone to keep on checking their own fate to make sure they’re not going to get screwed at some point, out of things.
Me: My theory is that the book is a living thing, so like most living things, they continue to move and change when you're not watching them. So even after Sentinel writes his changes, the book starts to evolve from there, changing the story as Sentinel isn't watching.
I think that totally fits. And it makes me think back to our
conversation about how Mercury might be the one who was making those
comics come to life and talk to their readers in the first two issues of
Glory. Living books are Mercury's whole deal!
FURTHER SPECULATION: Very little about how the book works is established, so there are a lot of possibilities. The book could have all sorts of mechanisms to protect itself: It’s possible that a person experiences physical or mental pain upon rewriting reality (“Mercury” poisoning), such that it takes tremendous force of will to continually rewrite it. It may get more and more difficult the more rewrites someone does, such that they eventually are too exhausted to keep making more rewrites.
WILDEST THEORY OF ALL: The Mercury Book we read about in Judgment Day is a facsimile, and the real one is still in the realm of Gods, at Mercury's nightstand. He gave the mortal world a fake one to play with that can still affect their reality, but ultimately if Mercury wanted to, he could rewrite the entire mortal universe, even going so far as to create new versions of reality wherein the book that some mortals THINK is the Mercury book no longer even exists. Perhaps he even already did this more than once, leading to worlds such as the one seen in "Blue Rose" or the one(s) seen in the 2012 relaunches.
Me: That is crazy, but I don't dismiss it. Why wouldn't the Blue Rose or 2012 revision happen from whatever the book was doing in the Awesome world at the time?
I don't know, it kinda came to me as I was writing, and I was thinking through some of the book's implications. At the end of Judgment Day, Sentinel threatens to write a line saying that the Citadel Supreme exploded, and only Sentinel survived. But Glory was on the Citadel at that time. Would she have died because of what Sentinel wrote in the book? If so, that means the book can kill someone who is from the realm of the gods. Which would mean the book could kill Mercury, theoretically. Would Mercury create a book that mortals could use to kill him?