by Robert A. Heinlein
Buy from one of these Booksellers:
Amazon Editorial Review
Earth was being invaded by aliens and the top security agencies were helpless: the aliens were controlling the mind of every person they encountered. So it was up to Sam Cavanaugh, secret agent for a powerful and deadly spy network, to find a way to stop them--which meant he had to be invaded himself!
Other books you might like:
37 Copies Registered