Are there any books you can think of that make a sudden, unexpected hard turn into sci-fi, or incorporates elements of sci-fi into a seemingly incongruous setting? If so, were you amused or annoyed?

Like for example, a standard domestic drama about a couple going through divorce. 300 pages in, it's revealed to the reader that the neighbor down the hall is an alien from Epsilon Eridani b. This fact is not at all shocking or novel to the couple, and story is still just about divorce.

Previous example doesn't exist, but for a sort of half-examples:

Not a book, but the movie Chicken Little. First half is about a bullied kid trying to make his dad proud by winning a baseball game. About halfway through it's suddenly an alien invasion movie. There is nothing foreshadowing this sudden genre change at all.