"I must not fear,” wrote Frank Herbert in “Dune,” his 1965 epic science-fiction novel. “Fear is the mind-killer.” Despite the fact that we now live longer and more pain-free than at any other time in history, that we are healthier than ever before, and that the world is arguably more peaceful right now than at any time in the last century, many of us are “mind-killingly” scared. We’re scared of everything from the food we eat to the death that awaits us all. But why are we so afraid, and what is the true source of all of this fear? The following five books explore the topic in various ways, each offering a chance to face — and possibly extinguish — our fears once and for all.