Take this book up to the counter to buy......
But in all seriousness, just strike up a conversation with her that feels natural. Ask her to show you some genre of books, and ask her if she has any favorites. When you ar reasonably isolated, tell her "You are fun to talk to. We should get together sometime when you aren't working." then give her your number.
IF SHE IS INTERESTED, she will text or call you. If not....ON TO THE NEXT ONE OL PARD!