John Brunner 
Skynappers [EPUB ebook] 

When Ivan Wright stepped out of his mountain cabin, rifle in hand, to investigate the sound of a strange helicopter, he stepped right into the middle of a galactic crisis. For the crew of that odd aircraft were not men such as he’d ever seen before – and when he tried to oppose them, he found himself hurled uncontrollably into oblivion. He awoke to find himself considered as a kidnapped barbarian from a backward planet in a galaxy of advanced civilizations – yet one who somehow held in his own hands the key to all their futures!