I've researched bugs on this quest and have not resolved the inability to access the location of Shalidor's writings when directed to Wolfskull Cave. I had completed the "The Man Who Cried Wolf" quest before I began the Shalidor's Writings quest, although I do not recall which of the two quests I received first.
Does the order I received the quests matter? More importantly, is there a way to fix this quest so I can retrieve the writings and complete the quest?
If it helps, I'm playing the PC version.