Add a comma after room.
If this character happened to have more than one father, and they’re both dead now, and the book belonged to both of them, the apostrophe would go after the s. Otherwise, the apostrophe goes before the s to indicate the singular possessive form of father.
Book of Shadows is normally capitalized (but not italicized — it’s not actually the title of the book, just its proper name), at least every time I’ve seen it, to make a distinction between a sort of journal kept by a witch, etc., and a book made of shadows or whatever those words would mean if not capitalized.
There is no such verb as pooring. I think the person who created this example knew that pouring was wrong but couldn’t think of any other homophone. (To young people in particular, pore is usually a noun meaning a small — but ginormous in appearance — hole or dimple, especially in the skin of one’s face. Tell them that pore is also a verb that has nothing to do with complexion issues, and they’ll look at you as if to say, I can’t even.)
She sat in a hidden room, poring over her late father’s Book of Shadows, seeking revenge.
(WordPress’ spell checker says pore isn’t a word at all. Go figure.)