Retroshock — D.W. Murray

Faced with the complex theories of time travel, Josh Kensington, a 25 year old genius inventor, is smart enough to know that his time chamber must never be used. But when a billionaire defense contractor prepares to open Pandora's Box by sending assassins back in time to alter the course of history, Josh knows there is no way to control the massive reality shift and his machine must be destroyed. Indeed he must destroy the reality of the machine itself.