Islam doesn’t teach something weird out of the normal. And the Quran doesn’t pretend to be an innovation. It is a confirmation of what came before. A reminder and a warning to the People of the Book.
Read what the Old Testament says about the oneness of God:
Deuteronomy 4:15-19, 23, 27-29, 35-36
Be very careful, then, because you saw no form at the time the Lord spoke to you at Horeb from the middle of the fire.
I say this so you will not corrupt yourselves by making an image in the form of any kind of figure. This includes the likeness of a human male or female,
any kind of land animal, any bird that flies in the sky,
anything that crawls on the ground, or any fish in the deep waters of the earth.
When you look up to the sky and see the sun, moon, and stars – the whole heavenly creation – you must not be seduced to worship and serve them, for the Lord your God has assigned them to all the people of the world.
Be on guard so that you do not forget the covenant of the Lord your God that he has made with you, and that you do not make an image of any kind, just as he has forbidden you.
Then the Lord will scatter you among the peoples and there will be very few of you among the nations where the Lord will drive you.
There you will worship gods made by human hands – wood and stone that can neither see, hear, eat, nor smell.
But if you seek the Lord your God from there, you will find him, if, indeed, you seek him with all your heart and soul.
You have been taught that the Lord alone is God – there is no other besides him.
From heaven he spoke to you in order to teach you, and on earth he showed you his great fire from which you also heard his words.
Deuteronomy 6:1-2, 4-19
Now these are the commandments, statutes, and ordinances that the Lord your God instructed me to teach you so that you may carry them out in the land where you are headed
and that you may so revere the Lord your God that you will keep all his statutes and commandments that I am giving you – you, your children, and your grandchildren – all your lives, to prolong your days.
Listen, Israel: The Lord is our God, the Lord is one!
You must love the Lord your God with your whole mind, your whole being, and all your strength.
These words I am commanding you today must be kept in mind,
and you must teach them to your children and speak of them as you sit in your house, as you walk along the road, as you lie down, and as you get up.
You should tie them as a reminder on your forearm and fasten them as symbols on your forehead.
Inscribe them on the doorframes of your houses and gates.
Then when the Lord your God brings you to the land he promised your ancestors Abraham, Isaac, and Jacob to give you – a land with large, fine cities you did not build,
houses filled with choice things you did not accumulate, hewn out cisterns you did not dig, and vineyards and olive groves you did not plant – and you eat your fill,
be careful not to forget the Lord who brought you out of Egypt, that place of slavery.
You must revere the Lord your God, serve him, and take oaths using only his name.
You must not go after other gods, those of the surrounding peoples,
for the Lord your God, who is present among you, is a jealous God and his anger will erupt against you and remove you from the land.
You must not put the Lord your God to the test as you did at Massah.
Keep his commandments very carefully, as well as the stipulations and statutes he commanded you to observe.
Do whatever is proper and good before the Lord so that it may go well with you and that you may enter and occupy the good land that he promised your ancestors,
and that you may drive out all your enemies just as the Lord said