A river called Time : a novel
(Book)

Subtitle from book jacket.

"The Ark was built to save the lives of the many, but rapidly became a refuge for the elite, the entrance closed without warning. Years after the Ark was cut off from the world--a world much like our own, but in which slavery has never existed--a chance of survival within the Ark's confines is granted to a select few who can prove their worth. Among their number is Markriss Denny, whose path to future excellence is marred only by a closely guarded secret: without warning, his spirit leaves his body, allowing him to see and experience a world far beyond his physical limitations. Once inside the Ark, Denny learns of another with the same power, whose existence could spell catastrophe for humanity. He is forced into a desperate race to understand his abilities, and in doing so uncovers the truth about the Ark, himself, and the people he thought he once knew."--Publisher's page.