Good book, if a bit dated.
Think "Freaky Friday" with aliens and espionage (and some sexual themes).
What if there was an alien race with the ability to switch bodies (with yours!) at the mere touch of a hand. Now a secret government organization knows, and is trying to duplicate tha ability for its own purposes. But there is a second alien race that can also do it, and we humans are caught in the middle of a potential war.