Gauntlet by John G. Doyle

Time travel, the power sought after and craved by everyone and held by none. Until now. Not only is time travel very real to Jericho, he’s used it in the usual ways one would expect—getting rich, predicting world-changing events and, more importantly, traveling to whenever he chooses just for kicks. But just when he thinks his secret is safe, he discovers two other time travelers. One politely wants him to stop while he’s ahead. The other wants to end time as we know it and bring the planet to the brink of destruction. So, no pressure.