His most provocative and experimental work of the sixties, Beautiful Losers affirms Leonard Cohen as a visionary songwriter and novelist.      Beautiful Losers is a novel of stunning prose that is equal parts vulgar, rhapsodic, and viciously witty. At the center of the story are three individuals, united by their sexual obsessions and mutual fascination with Catherine Tekakwitha, a seventeenth-century Mohawk saint. A bereaved narrator reconstructs his relationship with his deceased wife and best friend - a love triangle of two men and a woman with a capacity to betray each other repeatedly. As each character gradually succumbs to self-abandonment, their descent is paralleled alongside Catherine's history, whose self-destruction marked her ascendance to sainthood. In a thrilling marriage of profane and divine, this sensuous erotic tragedy examines the fine line between faith and desire, as the lines between the sensualist and the saint blur beyond distinction.