MATTHEW PEARL'S second novel is based on what he calls "one of literary history's most persistent gaps." Edgar Allan Poe died, Pearl tells us, "at the age of 40 in a Baltimore hospital on Oct. 7, 1849, four days after being found in distress at Ryan's inn and tavern." The stubbornly unexplained gap occurred in the five days preceding his appearance at the tavern. Poe was supposed to be almost a...