This book is not for atheists. At least not for atheists who have decided to be atheists without any further questions or research.
It is also not for believers who think they have all the “standard” answers that do not need updating or modification
Nor for believers who think that there are no questions at all. In short: it is not for the generally reassured, from both sides.
Not for those who are reassured that their atheism is the correct position, nor for those who are reassured of their faith and steadfastness and their lack of need for any kind of “mental” immunity.
These two opposites are certainly not equal, and we “envy” the second one for what he has.
But that doesn't change the fact that the book isn't meant for him either.
To reassure my mind, it is certainly not for these or those.