Spirit of Light
Be who ever you want
What you say is interesting i know some atheists do read religious books, but how then can some atheists not understand the word God? Thats the main issue in OPAtheists use the definitions of God(s) which comes from what we are told or what scriptures tells us about them. Anyone can pick up a bible or the Quran or some other religious text and read it and learn about how and what God(s) is according to these, you don't have to be a theist to understand these texts.
Think about how many Muslims, just to use them as example that believes in the word of the Quran, yet they don't agree on the meaning of it and are willing to kill each other due to understanding it differently. If theists were the only ones that could understand it and get a clear image of what God is, then they are doing a very poor job at it to be honest. And the same goes with Christians, Jews etc.
The main issue as I see it, is that when theists talk about God they are extremely vague in explaining what said God is. But I think if you asked theists of different religions, even within your own, to clearly define exactly what they believe God is, what he is capable of, whether he intervene in our lives etc. that you probably wouldn't agree with almost 90% of them. When someone uses the word God and explain their feeling about such God, such as him being loving or whatever, you would probably agree, but that person might very well be a Christian saying that, which doesn't agree on your idea of a God, if you go in details. The commonality you speak of, only exist due to the vague definition of God that people use, if you ask me.