According to its foreword, The Tragedy of Arthur is not a novel. It’s a heretofore- undiscovered Shakespeare play that comes packaged with a massive book-length introduction by ”internationally best-selling author Arthur Phillips.” Sound gimmicky? It is, but Phillips invests the metafictional gamesmanship with bracing intelligence and genuine heart. The fun starts with the opening line — ”I have never much liked Shakespeare” — and the energy never flags as the book develops into both a literary mystery and a surprisingly effective critique of the Bard. But the actual play, tacked on at the end, is a bit of a snooze. A?