I wasn't comparing new books to visiting new cities. I was comparing knowing the ending of a book to knowing where you're going on a trip. If I set out to drive to LA, I know where I'm going to end up, therefore I'm spoiled on the ending, but the trip is still worth taking.
Same thing. You know where you going to end up, but in a city as vast as LA, you'll be able to see very different things. So, in that case, the ending is what you see/do in LA, and that can be extremely different each time you go. It's as if the ending of the book changed!