Raunchiest/spiciest festive Christmas-y book?

My wife is in a Christmas reading challenge with a bunch of different categories. One of them is "Festive". She's been getting more into romance and smutty books lately, and calls most of them too vanilla. Was hoping to get her a book that fits her "Festive" category while also maybe being a bit over the top sexy. Or weird sexy. Or whatever, let me know what you can think of!