I seem to have run in to a bug where I cannot access the hidden area in which this book is found (following the map from Russetwood). I have a character with 11 mechanics who highlights the area purple, and when I mouse over the area my cursor changes to a glove. Despite this clicking on the area does nothing and so I can't access the tome.

 

I have tried verifying game integrity already. My wizard is waiting for shadowflame

 

Any suggestions?

Have you looked at the map? You need to actually open the map.