This book is not directed at atheists.
At least not those who firmly decided on atheism without additional questions or further research.
It is also not for believers who think they possess all the 'ideal' answers without the need for updates or modifications...
Nor for those believers who think there are no questions at all.
In short: it is not for those who are at ease generally, from both opposing sides.
Not for those who are comfortable in their atheism, believing it's the right stance, nor for those who are assured in their faith and stability, believing they do not need any kind of intellectual 'immunity'.
The extremity of these opposing sides is evident, and while we 'envy' the latter, this does not change the fact that the book is not directed at them either...
This book is certainly not for either group.