Because neither of them got a book for Christmas, both my wife and her mother feel like they are missing an essential part of the holiday. Here is what I'm dealing with:
For my wife, she will read most anything, but I think it's fair to characterize her favorites as epics. She sometimes calls "Pillars of the Earth" her favorite novel, but she also loved "The Stand" and the first two Kingkiller Chronicle books. I would love a rec in this vein.
For my mother-in-law, it is tough. She reads constantly, but she reads (for the most part) dreck. It's also strange that for such an educated woman (M.D.) she strongly refuses to read anything that can't be characterized as a "whodunit" or "spy thriller." While there are great books in these styles, they are not the ones that she reads. I could easily grab something from this genre, but (a) I'd be afraid that she had read it already, and (b) I (and my wife) would love to give her something that fits the conventions that she's interested in, but sneaks a good book to her. I don't know if this possible, but if it is, I'm sure this is the place to figure it out.