<p>The Edge of the Unknown is Arthur Conan Doyle's final major work, a collection of essays and articles delving into mysterious and psychic phenomena. Compiled in the twilight of his life, this volume finds Doyle investigating assorted "unsolved" mysteries?from the uncanny powers of Houdini to ghostly encounters and spirit communications. Written with conviction, Doyle uses each chapter to champion the spiritualist cause, offering what he sees a...