Ezekiel said the book has been stolen. Your best bet is to find the Ruffians and see if they have any information.
Ramdor? Hrm, let me think... Ramdor... Oh yes, the death priest. What does he want with the book? Well it doesn't matter. Yes I lied to you and no I don't have the book. Not anymore, anyway. It was stolen. Probably by one of those filthy refugees.
Besides, Auchindoun is now defunct. We have no use for the book. If you find it, you can keep it.
Like I said, I saw some of those ruffians snooping around the terrace last week. Start your search with them. They're probably playing dice in the slums.