What if John Wilkes Booth wasn't killed in that blazing barn? What if he survived, went into hiding, disguised himself as a N.Y. waiter, and became the lover of Mrs. Chester A. Arthur? Furthermore, what if an elopement plan by the lovers went awry--leading to Chester's death, Booth then impersonating Chester. . . and, in that role, becoming VP and Prez of the United States Those are the increasingly implausible premises of this literate, overlong fact/fiction--but if Wiegand (author of more serious novels in the Fifties and Sixties) never manages to parlay his imaginative notions into credible conspiracy-suspense, there are diverting touches and engaging textures along the way, Best by far are the opening 100 pages: an effective Civil War-period sketch of General Arthur's uneasy marriage to Southern belle Nell; Booth's escape, aided by Arthur's Republican cronies (co-conspirators in the assassination!); his explanation of the Ford's Theatre shooting (an attempted kidnap that went fatally awry!); his hiding-out with Nell's Virginia relatives, their affair (nicely understated), and his move to N.Y.--waiting on tables in heavy disguise at Delmonico's, where he comes face to face with stunned brother Edwin. Then, however, comes Booth's plan to fake Nell's death and flee with her to France--a scheme that's already half-accomplished when Chester learns of it and drops dead from shock on the spot. What to do? Well, with help from those corrupt political cronies (who periodically try to kill Booth), the fugitive miraculously becomes Arthur, runs for VP with Garfield, inherits the White House, tries to balance his role-playing with his Southern sympathies--but is forever obsessed with finding the ""Fredericksburg File,"" suppressed papers that will prove The Truth about Ford's Theatre. (This file-quest becomes increasingly tedious.) Meanwhile, supposedly-dead Nell hovers, hides, goes mad, etc. And there's a faintly Dickensian subplot involving Booth/Arthur's valet Raymond--a former male prostitute who keeps getting into trouble while worshipping Nell's little daughter. Even on its own terms Wiegand's historical fantasy is full of inconsistencies and unconvincing motivation (e.g., the behavior of the Arthur children). Nor does he write with the brio that might have made this an unabashedly contrived romp. But fanciers of historical crazy-quilts will find stylish, leisurely, well-researched diversion here--at least until the plotting buries all its panache under earnest, belabored complications.