The line between being daft, eccentric or bonkers is a thin one indeed. Black Bart’s reputation as a skilled stagecoach robber largely hinged on the fact that he simply strolled away from the scene of his crime on foot, and the posses tracking him always assumed they were looking for a horseman. Eccentricity, dumb luck, or didn’t he know any better? In Carl Sifakis’ American Eccentrics (Facts On File: $17.95), 140 of the country’s more notable dingbats are examined in passing--with the author, happily, making no attempt to explore why these people acted as they did. Lizzie Collins, for instance, could have been one of New Orleans’ more prosperous prostitutes if she had collected money from her clients instead of their trouser buttons.