The book's opening isn't labeled as an introduction, but whatever you'd like to call it, the few paragraphs before Chapter 1 set the scene for the story to come. If you think you're reading a romance that ends in "happily ever after," the first sentence will set you straight: "He'd stopped trying to bring her back" (P.1).
Even though we don't yet know who "he" is, this sentence tells us a lot. Our "he" once had someone he'd felt strongly about, and he'd lost her. Not only that, he'd given up on bringing her back. What a way to open a book.
The girl described in the prologue—Eleanor—seems like a strong character before we even meet her. She haunts our unknown protagonist's memories, red-haired, "standing behind him until he turned his head," and "ruining everything" (P.8). Even though it seems like this will end in disaster, we can't wait to meet her.