Brother I would advise you to look into this person "Zakir Naik" he has alot of videos you might find interesting, why don't you take a look there.
Every religion has their own book.
The Christians have 1 but with so many different translations, why is that ? They all believe in that 1 god, so why don't they unite those books into one ?
In India it's the same thing with multiple religions with many sub categories.
Now to your point, as I see that you are a true seeker, I hope Allah will prove to you his existence some day.
Then We made the sperm-drop into a clinging clot, and We made the clot into a lump [of flesh], and We made [from] the lump, bones, and We covered the bones with flesh; then We developed him into another creation. So blessed is Allah, the best of creators.[23:14]
Now I want to ask you, as you deny the existence, could you tell me who created it ? Tell me what is your logic here so I can understand you better.
Allah has given us 4 books which he scattered across the world for different tribes. As Muslims we all believe in all those books, tawrat(Torah, for the jews, Enjeel(bible, for the Christians), zabur(book of dawud, pre-islamic Christians), Quran(Muslims, for all man kind).
We Muslims believe in all 4 and those who don't believe that aren't true Muslims but now the problem here is that the Bible, Torah, zabur (not too sure about zabur, I don't know much about it) have all been altered, changing the words of God (again, I understand that you still need proof of him).
To our knowledge a god is a perfect, absolute being.
And then when you look at the Bible you'd see people categorizing themselves with different groups even thought they all follow the same god, now how can this be, if god is perfect, how come he allowed such a thing to happen ? When you say Jesus powers were through god, so who is god ? Mind that also, if you go read about it, Jesus was never killed and crossed! But he was raised into the heavens (another topic).
Many other religions are similar.
I'm not too sure but there is the possiblility of religions other than (Islam which possesses the same one book, no different translations, the exact point of view anywhere you go (whether the people speak English, Urdu, Bengali, arabic they all translate to the same thing) ), other religions probably have the same thing but I don't know, the Buddha's have their own unified believe but I can't give you an explanation there (my knowledge is limited), I'd seek Dr. Zakir Naik! He is the one you need to answer your questions, he is a logical, scientific man and loves to debate! I'd really look him up if you are interested.