How do you define “atheist book”? As others have said, since atheism isn’t a belief system, there’s no need for a book to describe it.
Expanding the definition a little, here are some well-known books on the atheism topic and/or written by atheists:
The God Delusion by Richard Dawkins
God is Not Great by Christopher Hitchens
The End of Faith and Letter to a Christian Nation by Sam Harris
Why I Am Not a Christian by Bertrand Russell
Godless and God: The Most Unpleasant Character in All Fiction by Dan Barker
There are many others, but these are a start.