'What's the good of a book without pictures or conversation?' Alice demanded. Her creator, Lewis Carroll, made a point. OK maybe we can forgo the pictures but a book where non of the characters speaks (or very little) makes for a monotonous read. Writers who employ mainly narrative are unconfident (I suspect) of writing realistic dialogue. It's a pity because it is a powerful tool, not only giving characters voivces but telling the reader a lot abut their character, background location, mood, thought process, feelings...need I go on? I've never found writing dialogue difficult but for those who do my advice is this: cultivate being a listener, tune in to people's voices. Keep a notebook and write down scraps of dialogue overheard. And here is the big one: eavesdrop on conversations whenever you are in a public place. Eventually the music of dialogue will enter your brain and you'll find yourself writing convincing and realistic dialogue.