So did you followed the ghost up to a door that has a magical seal on it ??? Then the ghost takes the path downstairs, keep following him and you will end up on a "secret" -it isn't really that hidden- wall-door that you have to open with a lever. There the ghost sits next to his corps, the skeleton doesn't hold the verse it only has a hand over the book, it should be right there and visible, if it isn't then it glitched and went through the ground.

Only way to fix that would be to load a save file before entering the dungeon or maybe even just a previous area of the dungeon -separated by a door with loading screen this is- and follow the path until you reach the area again, if the book doesn't appear then it is a glitch.

If that is the case and the book is unobtainable then your only choice would be to load a save previous to getting into the dungeon.

Try loading a save previous to entering the location, it is your best chance. And if the glitch persists, leave the area and wait 10 in-game days before coming back. Some locations require 30 in-game days.

That's the time needed for a standard location to be reloaded with all its items so during this reload you might get lucky and the book might respawn in the proper place.

BUT ONLY IF YOU HAVEN'T VISITED THE DUNGEON YET THE QUEST ITEMS WILL RELOAD, loading a save before entering is what is important.

Loading a save before entering and then waiting enough time - preferibly away from the location's entrance - are your best shoots to fixing the problem.

HOPE THIS HELPS - AND GOOD LUCK !!!