Atheism requires only one thing, disbelief or lack of belief in the existence of God or gods. Nothing more, nothing less. What is to investigate.
With all respect, it is not that simple.
Atheism is thousands of years old stance. Embracing atheism will leave you with philosophical questions that you will never find answers to.
Ancient atheists were globally recognized philosophers who honestly tried to solve these questions.
Just compare this to "the Delusion of God"
There is no comparison.
By the way, I used to debate atheists before.
However, I reached a conclusion that many atheists are atheists by choice.
And for many of them, it is like taking a stance against a God who is the end cause of their suffering, so in retaliation they decided to deny his existence!!
Currently I rarely engage in such debates.