A delusion could be schizophrenia--someone that can't tell the rationally
known things from otherwise. A person can believe in God knowing it's a faith
in a possible God beyond the rationally known see-able, etc., things and be just
as reliable regarding the see-able etc. things as someone who doesn't.
Dawkins' stance is that a supernatural creator almost certainly does not
exist, etc.
For a better thought-out book on the possibility of the basic God idea, I
recommend "How to Think about God" by Mortimer Adler.
http://en.wikipedia.org/wiki/Mortimer_J._Adler#God
Beyond that it's faith. You can know it as such whether you choose to have
it or not.
Dawkins' stance is that belief in God leads to being against science, fanati-
cism, bigotry, etc.
But someone can know the God concept is a faith choice and not mess with the
see-able, etc., whether they believe in God or not, or mess with the see-able,
etc., such as to propagandize for their priority group, whether they believe in
God or not.
Someone can be too 'centric as to be intolerant or worse to others whether
they believe in God or not, or not be too 'centric whether they believe in God
or not.
Someone can cause unnecessary hurt or death whether they believe in God or
not, or not do that whether they believe in God or not.
The main problem is the believers and non-believers who propagandize, are too
'centric, and cause unnecessary hurt or death. We don't need everyone to not
believe in God anymore than we need everyone of one race or nationality for a
more peaceful world. We need people to not propagandize, be 'centric, or cause
unnecessary hurt or death whichever of those categories they're in otherwise--to
be more relaxed about the different categories otherwise.
Where Dawkins goes beyond those things to make a case there shouldn't be
believers in God for the world to be better, he's ironically being 'centric,
and the 'centric ones of the believers and non-believers have caused the most
problems.
When doing so, he's being as boring and preachy as any preacher who bored the
flock asleep with another sermon of 'centric propaganda about how everyone
outside his group are the bad people.
Metacritic reported the book had an average score of 59 out of 100. That
sounds about right.