I think this book dates from the 60s or perhaps 70s.
A brief synopsis: In the book a man appears, apparently from the distant future, I remember he had a single name which I think may have also been the title of the book.
Very soon he is followed by thousands of people around the world, almost like a messiah. He is taken on tours of the society (which I think is already set somewhat in our future) and appears to be completely pansexual and somewhat amoral.
I know he stays with a couple at their home but ends up ruining their relationship as he sleeps with both of them unbeknownst to each. Eventually he attends a huge rally where he walks among the people, supposedly protected by a force field but it seemingly breaks down and he is swamped by the crowd.
The husband in the book seems to see two people reach out and grab the man and he thinks it possible he has been 'arrested' by his own people and taken back to the future.
Ring any bells? Any help greatly appreciated.