In his early role as Lucky Jim, Kingsley Amis declared the awkward essence of his personality. "I'm the boredom detector". That ability, or affliction, qualified all his other propensities, even the one for multi-targeted amorous desire. In Zachary Leader's long, thorough and generally judicious new biography, its hero's spasmodic quest for emotional satisfaction is rarely out of the picture. The novelist, poet, critic, teacher and bibulous clubman we more or less frequently meet, but the man with sex on his mind we seldom escape. Journalists understandably find this material an alluring compost in which to burrow.