Hands down, the beginning. But not the first few pages, the beginning third of the book. I love the excitement of getting to know the characters and connecting with the storyline. It's the beginning of a vacation to a new land.
Totally different opinion when I'm writing a book. I enjoy the beginnings of putting a story together, but I also find them the hardest to write. The middle is tough, too. My favorite parts to write are the meat of the story (from halfway to almost the end).
But, then there is the dreaded ending. My book club friends will tell you, we complain the most about endings. Either they wrap up too quickly, fall flat, or disappoint. Rarely do we all agree that an ending worked or made the story better. Knowing this, I find writing endings especially stressful.
I would love some other thoughts, from both readers and writers. What's your favorite part of the book? The start or the end? Does it change as a reader versus a writer?