Usually only takes 1-2 days.
I've had them hold books up because of cover artwork on a book jacket (there was a Star of David on the cover of one mystery/murder novel as the plot involved a Mossad secret agent) as well as because of the title of another book (Why I am not a Muslim). They refused to release that book and I had to send it back ouside of Qatar at my own expense (silly, really, because I just brought it back in my luggage on my next trip).

So be patient...it's more a hassle than anything else.