This is funny because books are about the only thing I really feel compelled to finish whether I like it or not.
I've abandoned countless side projects, instruments, sports, meals, friendships etc when they stopped holding value for me.
But once I crack open a book I really feel like I have to finish it before I can get on with my life. I don't start a lot of books anymore but they tend to stay on my todo list until I've literally read every word..