This is a mystery that might interconnect everything that has happened, is happening, and will happen.

Answer A: Jorge Luis Borges

Answer B: It dosen't matter who originally wrote it, since its been retconned and rewritten so much its impossible to read

(Translation: its all dependent on the writers and editors at DC, and they go back and change things often)

destiny's book writes itself. it (they) is/are/will be destiny.

(bored on a sunday, i start going thru other forums)

Destiny's Book does not write itself, only because it already has been written. Destiny's Book probably came into existence along with him, by then the whole book was already written. It may be who wrote it can explain the mysteries of the universe.

destiny's book is not already written. it shifts and changes with all possibilities until destiny becomes the present then the past.

True, that it shifts and changes, but the fore-written presumably shifts and changes according to what is happening at the present. Although Destiny is fate, he also represents freedom. This may seem almost paradoxical, but there were already written things in the future. One example is when wind accidentally blew Destiny's Book's pages forward to when Daniel just became Dream, just before Destiny adjusted back to the right page. Destiny's and his book's knowledge of what was, is, and will be. But since the future is the most varying, the fate changes according to the present freedom to change events.

Something else to mention: this little quote from The Wake.

"The people moved as if their every move were forordained, as if they had no true will of their own.

As if their every action were written long ago, in a book.

But then, there are things that you do not know, brother, and things not in your book.

And I'm dimly certain that there is a moment in Season of Mists when Destiny is surprised. Perhaps he doesn't read ahead (wouldn't you though? What's the point of being a dull guy in a robe in a garden who has to be all sombre if you can't also go "Hey, guys, I know who Morpheus' secret girlfriend is - it's Thesally!"

his book can't change its the future its not what might happen its what will happen

Does it really matter? Destiny's book is EVERYTHING--everything that HAS BEEN, WILL BE, and IS...and I suspect some things that have not and never will be thrown in for good measure.

I imagine Destiny was created with his book already written, and chained to him. As if at the very start of the Universe's motion, everything was...well, simply WAS.