HENRY VIII. By Jasper Ridley. Viking. 472 pp. $24.95.

HENRY VIII has long been a favorite subject for biography. In his youth, he was the idol of his people, as fine a sprig of chivalry as ever broke a lance in joust or danced a gay galliard. In his middle age, for a woman's love he wrenched his country out of the mainstream of European life and thereby helped to chart a new mainstream for the whole world. In his dotage, baffled, sick, and thwarted in his short-sighted personal ambitions, he made life spectacularly miserable for everybody he touched, from his worst enemies and meanest subjects to those around him who loved him and could have given him comfort.

Any biographer approaching this well-worked ground must offer some special argument, some new viewpoint, not merely to give the matter frehness, but to keep it all under control. So much is known about Henry, so much conjectured, that a writer venturing in without a gameplan will be overwhelmed, and this seems to have happened to Jasper Ridley.

Research is Ridley's strong point, and he marshals a vast and entertaining array of facts and names and dates, particularly about what we would call Henry's foreign policy. This is the real value of most histories: to give the reader sufficient information to allow him to form his own opinions, and Ridley provides lots of matter.

Yet he never builds up a large picture of what was going on in Europe in the 16th century, or even, in a useful sense, what was going on in England.

His focus is too tight on Henry. Sometimes the focus is so intimate that it gives this biography the tone of a gossip column, as when Ridley spends nearly three pages discussing the elopement of Henry's sister, Mary Tudor, with the rake Charles Brandon. By comparison, the Battle of Pavia, where the balance of power in Euope swung decisively toward the Emperor Charles V and away from the kings of England and France, receives half a sentence.

Nonetheless, the 16th century is always exciting reading. Ridley tries to show Henry as a real macho sort of guy, always in control, but his opinions cannot obscure the facts, and the facts allow for a more complex Henry, and a more interesting one.

RIDLEY SEES Henry as a formidable and resourceful politician. Yet Henry did only what English kings ordinarily did: he tried to fatten at the expense of France, he strove to increase his control of the English church and his independence from the pope.

No evidence at all suggests that he understood how final and irrevocable his split with Rome would be; English kings had been defying the pope for centuries without permanent damage to their Catholicity. Fiddling with his domestic arrangements, Henry accidentally made a revolution that he spent the rest of his public career striving to deny.

In fact, Henry's failures, more than his successes, shaped the English future. He behaved as if he were still fighting the Hundred Years War, but political realities had changed since the Battle of Agincourt. Against the high-powered absolutist monarchies of the Hapsburgs and the Valois, Henry could gain no advantage; his inability to meddle successfully on the Continent led the next generation of Englishmen to turn their backs on Europe and follow their ambitions across the ocean.

Ridley writes with energy, if not elegance, and the book is full of anecdotes and choice pieces of historial business. Perhaps too full: Ridley often attacks his subject in a breathless rush, jumps disconcertingly from scene to scene, subject to subject, name to name, without much transition. Nonetheless, history buffs will find this an interesting and entertaining book, worth the reading for the sake of the 16th century.