Homegoing by Frederik Pohl

Sandy Washington was a pretty normal guy. The only unusual thing about him was that Sandy had been raised by aliens on their spaceship. The Hakh’hli had done everything they could to give Sandy an Earth-type boyhood. Now, finally, the Hakh’hli were bringing Sandy home to Earth. And while they were at it, they intended to give humanity some extraordinary gifts. The Hakh’hli seemed to have Sandy’s & humanity’s best interests at heart. But the people of Earth weren’t so sure.