We have a great game that we play when we go up there with friends, a bit like the Dictionary game/Balderdash. Everyone peruses the shelves a picks out a promising book. Then, one round at a time, someone gives the title of their book, reads the back, and maybe reads a few choice paragraphs from the middle or end, giving everyone a sense of the book.
Then everyone writes down an opening line on a slip of paper. The book-holder writes down the real first line. The slips are shuffled and the book-holder reads each of them, preferably dramatically. Everyone votes on the real one.
Writing first sentences is such a delightful exercise. And of course with genre fiction everyone has the license to go completely over the top. With the right group of people it's utterly hilarious, and it's amazing how frequently someone writes a sentence that seems better than the original.
(A random one I recall: a pot-boiled detective noir novel, involving a murder victim named Sunday: "If Sunday had known on Monday that on Tuesday she'd be dead, she would have made several different choices.")