Why would God limit something so important (the revelation of himself) to the pages of a book that depicts the history of one little tribe and their mythology about the origins of man and God?
And then further limit that single most important message for all mankind, to one guy from that tribe?
Then, to add insult to injury, allow all the original documents recording these events to be lost, allow a bedraggled set of letters and disparate writings to be pulled together 300 years later, a collection that no one at the time agreed on anyway, and then the language that most of it was written in dies so no one really knows what half of it means anyway?
1700 years later, no one is any the wiser and keeps fighting over what the collection of writings mean, and keeps continually fragmenting into more and more groups, cults, movements etc.
Meanwhile the rest of the world, the majority of the world, from way back when, has no idea all this is going on, or any idea that they have been left out of the most important revelation to all mankind. And the majority of the world still have no idea, because the keepers of this book are still busy arguing over it all, and billions of people, meanwhile, have missed out (and will continue to miss out) because God is stuck with this mess and isn't powerful enough or has his hands tied, or whatever, so he has no choice but to let most of mankind slope off to hell.
To make matters even more difficult, the keepers of the book have developed an extremely complex system of justifications as to why its the only source of everything God has spoken to mankind, using systems of very intricate circular reasoning, and then wrapping that reasoning in varying degrees of authoritarian control by presenting themselves as the ones who understand and can interpret it on our behalf.
Of course, because of all the endless divisions and arguments amongst the keepers, there are thousands and thousands of wise sages all dispensing conflicting understandings of the book with just as much authority and control, leaving the rest of us trying to decide who we should believe.
And that's just the tip of the iceberg.
Mind you, we do have a choice - we could take a step back and see if maybe there is a bigger picture?!