The ending of a book is, in my experience, both the best and worst part to read. For the ending will often determine whether you love or hate the book. Both emotions lead to disappointment. If the ending was good, and the book was worth your time, then you are left annoyed and depressed because there is no more book to read. However, if the ending was bad, then it's too late to stop reading. You're left annoyed and depressed because you wasted so much time on a book with a bad ending. Therefore, reading is obviously worthless, and you should go spend your time on other, more valuable pursuits.