EASY SILENCE.(Review)(Brief Article)

ANGELA HUTH. St. Martin's/Dunne, $24.95 (352p) ISBN 0-312-26812-2

"Suddenly William was able to contemplate the fact quite calmly: he would have to murder his wife." At the start of this unusual portrait of a British marriage, middle-aged William Handle is far from entertaining such wicked thoughts. For years, he has been happily married to Grace. Husband and wife each have their own satisfying occupations--William is the principal violinist of the Elmtree Quartet, and Grace is a painter--and they live comfortably in a suburb west of London. But then a new viola player--the attractive Bonnie Morse--joins William's previously all-male quartet, and William loses his …