Bob Shaw 
Shadow of Heaven [EPUB ebook] 

Those who tried never returned, and those who didn’t, always wondered what they were missing by not attempting the perilous journey to ‘Heaven’.The official designation of the giant anti-gravity floating disc was ‘International Land Extension U.S.23’. But to the people living like sardines in the fam-apts and dormitories on the ground below, it was known as ‘Heaven’.Government regulations meant that it was almost impossible for a human being to get to ‘Heaven’ — almost, but no quite, as Vic Sterling found out when he began to hunt for his missing half-brother Johnny Considine. For Johnny, along with over a hundred other rebels, had decided they could no longer stand the living conditions on Earth and had hitched a ride to ‘Heaven’, a ‘Heaven’ full of unexpected dangers for Vic when he decided to follow.