The vogue for memoir, like all vogues, comes and goes. But the impulse perseveres. Celebrities, addicts, abuse victims, politicians, soldiers, grieving children: Everyone has a story to tell and a conviction that the world wants to hear it--and often enough, if the best-seller lists are any indication, the world does.
Novels have to primary sources: writers' life experiences or their art experiences--although I suppose more religious writers might also make room for divine inspiration. While it's popular in publicity to focus on the life experience that informs a book, a writer's art experiences are just as responsible for how a story emerges from the imagination and eventually appears on the page. As Cormac McCarthy once said: "the ugly fact is books are made out of books. The novel depends for its life on the novels that have been written."