Recounting over 2,000 years of daft despots, raving rulers and potty potentates, this unique look at the world's craziest kings and queens will leave you shocked, amazed - and often in fits of laughter.   From the madness of ancient Rome, exemplified by the Emperor Caligula who wanted to appoint his horse to the consulate, we go on to meet Charles VI of France, convinced he was made of glass, Queen Juana of Spain, never separated from her late husband's coffin, and King Otto of Bavaria, who tried to ward off hereditary insanity by shooting a peasant a day.   Throughout history, royalty and scandal have gone hand-in-hand like a Prince of Wales and his mistress - witness the pocket-picking Farouk I of Egypt, Augustus II of Poland, who fathered an estimated 355 children, only one of whom was legitimate, and, more recently, Britain's master of tact and diplomacy, Prince Philip. From kleptomania and incest to transvestism and even pigeon fancying, all these and many more colourful characters can be found in this revealing trawl of the world's royal families.