The word "love" in the subtitle of Robert Farris Thompson's new work reflects the passion that the author feels for his subject. Actually, it would be more correct to say subjects, because he has gone far beyond the conventional notion of tango. His book is an energetic, vivid account of the music, movement, poetry and songs that evolved into the beautiful, difficult and sensual dance that is tango today. "It was the fabulous dance of the past hundred years," he writes in his preface.