I'm trying to find the title of a book I read sometime between 85 and 95 in German. It could have been written much earlier, and it was most likely translated from English. I think it had a "book to the movie" sticker on the cover, but all googling for the movie or book failed so far.
What I remember:
- brain transplants are safe and affordable enough to rent a body for a holiday. This is achieved with a robotic surgeon removing the brain and spinal cord from the old body and reattaching all nerves in the new body.
- an overweight guy leaves his dominating mother to take a holiday on a space cruise, renting a new body for the trip. I think through a bribe he manages to rent the body belonging to an assassin that was held in storage while the assassin was on an assignment. At some point a small alien is revealed to be living in one of the legs.
- the assassin returns from the assignment and gets the body of the overweight guy to follow him onto the cruise to get his body back. He later discovers that the body contained an implant producing a permanent feeling of guilt.
- overall villain is a human-alien hybrid that has a robotic container attached to his spine that contains four additional brains. He owns the cruise ship and I think he tries to crash / blow it up somewhere. Though details are getting fuzzy, there.