Why not simply show himself to humans? Why all the mystery? If communication is indeed what is needed, why not communicate in a more direct way instead of in a way that can be doubted?
He doesn't.
If you want to talk to God, you can.
If you want to see the manifestations of God, you can.
In fact, you have almost certainly already talked to God. Frequently. You have just not understood that that is what you were doing.
He isn't hidden. But he isn't what you want. You want a point source, a THING you can point at and say "That's God!" But God is "thing" that has numbered the hairs of your head, and not a sparrow falls in the remotest jungle of the world without God's consent. God isn't a point source. There's no "There" there.
Look at the natural law, functioning everywhere, perfectly, at the sub-microscopic and trans-galactic level. That law IS God.
He talks to you - you don't realize that your "inner monologue" is not a monologue at all, but a dialogue - until he stops talking to you and you find that even the interior of "your own" mind isn't really YOU. You, alone, cannot speak to yourself even in your head. That has always been God there, talking back with you, arguing with you, helping you reason things out.
Miracles happen. By miracle, I mean that the laws of physics, the laws of nature, are suddenly broken on your behalf. You know it, the outrageous "lucky strikes" you've had. You reason away that this was "just luck", but there is no luck in a world ruled by natural law, which is God. No, that's God simply choosing to alter the normal functioning of a "rule" for you - for the rule is him, and the "exception" is him. It's all him, all the time.
You SEE it, which means you SEE him, but he is too big and too all embracing to comprehend and cope with.
You've been talking to him all along, but again, he is so...MUNDANE...that you think he's YOU, you think your mind is just you running on talking with yourself. It isn't. Your interlocutor has always been God - although malign lesser spirits can also get in there if you crack your wetware with drugs and the like.
The major and minor miracles of your life, and other lives, everywhere, are him.
What you want is for God to send out a pseudopod and address you face to face, on your terms.
Sometimes he does THAT too. You've met people who have talked to God directly in clear and direct manifestations that stood out from the background. Jesus was the most dramatic of those cases, speaking to all, but individuals experience it in all ages.
You're not one of them, but if you encounter somebody who is and tells you so, you dismiss him as crazy.
So, you want God to manifest himself as a "pseudopod", so you can talk to a visible "thing". What do you want from him? What will you ask of him?
I demanded that he prove he was God by turning on the lightswitch across the room. Instead, I was thrust into the abyss, had him STOP talking to me internally - which is why I suddenly realized that he had been there all along - and then rip me out of the abyss and show me one gate of the glorious City, high above.
And his words "You have your answer."
So, that's what you want. The proof. Ask and you shall receive. You have to persist a little, like the widow and the unjust judge. God doesn't play parlor tricks.
Understand that your life will never be the same, because you can never un-see what you have seen, you can never un-believe what you know to be so. And understand that your fellow humans will treat you like [bless and do not curse][bless and do not curse][bless and do not curse][bless and do not curse]e if you try to talk to them about it. Either they don't want to know, or they think they already DO know, and they'll start quoting to you out of their books.
Do you want to be estranged from your fellow men, to get satisfaction on a question? You might think you do, but what is God telling you? You're already talking to him, all the time. So talk to him.
If you really have to have the pseudopod, like Thomas, then you can. Remember what happened to Thomas. He would not believe unless he saw. So God showed him. Then what? Then Thomas had to go out and be an apostle and preach. He went all the way to Parthia, then into India. Could he walk away? He knew it was true - how can you hide from what you know is true? And when they came for him in India, to ram spears through his body to kill him, his knowledge of the truth didn't spare him the pain and terror, didn't persuade his tormentors of anything - and pointedly, death is part of the process by which God runs the world, He's not going to SPARE your life no matter what, lest you remain the caterpillar forever who does not die in the chrysalis and be born anew as the butterfly.
Knowledge was perhaps solace to Thomas as he was being speared to death, but it didn't spare him anything. And it meant that he could not blanche and run away and hide. He had to go through with the whole grim thing.
So, God doesn't really hide himself, people are just not seeing and hearing what is in plain sight and hearing. He is communicating with you directly, all the time, but you don't recognize him. If you want to see and hear more clearly, you can, but once you have, your freedom is clipped off considerably for the rest of your life, and you will have a real hard time getting along with other people. Do you REALLY want that? Is that REALLY good for you? Apparently not, or not yet, because God hasn't grabbed you yet.
But if you really want it, you certainly can have it. It will not make you powerful, and it will not make you a leader - in fact, people who are already leaders, on human terms, will deride you if you talk about it, because you have something they don't.
It will not make you happy either, for then as you continue to experience the bruises and bad things, you will be talking to God as God lets those things happen to you. You will find yourself like the teenager talking to the parent: It's UNFAIR!
The problem, though, is that it is perfectly fair - you're just not a special snowflake. And it sucks to be told that by your Creator.
Still, if you want it, you can have it. You just have to ask and keep asking, and God has to decide he doesn't like you enough to actually give you what you want. Then your life will be harder.
It's much easier when things are left in the abstract and maybe.
On balance, it's still better to be closer to God than to get along with men - but the price of what it is that you want is that you will find an almost unbridgeable gap with other men, you will find yourself a freak, and others will too, if you talk about it. And many others will really HATE you for it, and call you names.
Want to talk to God right now? Engage in the inner dialogue, and you will see what I am talking about.
There is your answer as far as it can be conveyed. To really SEE, you have to go the rest of the way yourself.
Your book won't help you get there. But you will find, once you've gotten there, that the landmarks are as the book says. The book contains the truth, from the perspective of other eyes and minds. Your own eyes and minds will find different things fascinating than they did. And you'll find that nobody else in the world wants to hear your viewpoint. So you're left at the end talking with God.
Don't say that he doesn't show himself plainly. He does. You just are not seeing and not hearing what is there. There's a roadmap, if you really want it.