From the historian's standpoint, the worst thing that ever happened to Louis IX of France was his canonization. As soon as Louis was declared a saint, he fell into the hands of the hagiographers; and it has taken almost seven centuries for him to escape from the realm of pious legend into that of historical fact. Under Miss Labarge's deft hand, Louis becomes a saint, indeed, but a paradoxical one who, by modern standards, exhibits some strikingly unsaintly traits. Louis was, it is true, a mystic-but a mystic who could suggest that the best way to resolve a theological argument with a Jew was to kill the Jew, and who regarded the slaughter of Saracens as the key to eternal bliss. As an unworldly ascetic, Louis could, after he had fulfilled his royal duty by providing an heir, decide to lead a life of absolute chastity (the reaction of the Queen is not recorded), while plying his trade of king with such alacrity that he became, as even Voltaire conceded, the man ""destined to reform Europe, had it been capable of being reformed."" Saint Louis is certainly the soundest, and the most readable, biography of one of the dominant figures of the thirteenth century. It will become the ""standard"" in English and be welcomed by the student and scholar as well as by the general reader.