Rewinder

Denny was born into one of the lowest rungs of society, but his bleak fortunes abruptly change when the mysterious Upjohn Institute recruits him to be a Rewinder, a verifier of personal histories. The job at first sounds like it involves researching old books and records, but Denny soon learns it's far from it. A Rewinder's job is to observe history. In person.--from back cover.