Theodore Sturgeon 
To Marry Medusa [EPUB ebook] 

It came from outer space . . .The Medusa, the intergalactic conqueror, a hive-like being with a consuming appetite to absorb all life in the universe.Now the Medusa had reached Earth. It had taken control of its first human being. Through him it would possess all his fellows.But there was one thing the Medusa had not reckoned on. One tiny factor in the complex human equation. A desperate last chance for the stubborn and independent creature known as Man to save himself . . .