What if. . . the appeal of speculative history is felt not only by laymen looking for a good yarn but by professional historians as this entertaining volume shows. Harold Nicolson, Charles Petrie, G. M. Trevelyan, G. K. Chesterton and Hilaire Belloc along with nine other eminent British scholars indulge themselves in delightful mock-serious flights of imagination, rewriting the past to show what might have been or should have been. If only the 15th century Moors had resisted the armies of Ferdinand and Isabella, Granada -- blessed with Arabic science and medicine -- might have developed into an oasis of culture and civilization, a refuge from the Inquisition, beckoning to free spirits from all over the continent. If only Byron had not perished at Missolonghi he would have been King of Greece ""an affable but somewhat nebulous old gentleman bearing an almost startling likeness to King Louis Phillipe of France."" And Winston Churchill pursuing his pet notion of Anglo-American unity reconstructs how this blessed event came about as a result of Robert E. Lee's momentous victory at Gettysburg. One piece, A. J. P. Taylor's ""If Archduke Ferdinand Had Not Loved His Wife"" is in a somewhat different category from the rest. Taylor, always fascinated with the flukes and random contingencies which precipitated great events, argues quite seriously that but for Ferdinand's love for his Sophie he would never have attended the military parade at. Sarajevo, and without that fateful assassination it is indeed doubtful whether World War I would ever have happened. But Taylor excepted, this is a saucy, sardonic exhibit of serious historians at play.