Nonprofit chronowar : book three of the Jack Commer series
(Book)

Ranna Kikken creates The Committee to End Suffering on Planet Earth, but its first conference in 2020 is ruined when ex-astronaut Joe Commer time travels from 2036 to lecture Ranna's nonprofit ladies on the coming breakdown of the solar system. Tormented by his role in dropping the superbomb that ended the Final War but rendered Earth uninhabitable, Joe has quit the Space Force, much to the disgust of his older brother Jack, Supreme Commander of the United System Space Force. In the audience, feckless young Urside Charmouth is horrified by the revelations from the future, fearing that he's harmed the timeline with his own drug-like time travel experiments. He drags his unsuspecting girlfriend, Mandy, on an irresponsible time travel romp to 2033, where he finds proof of the coming destruction of Earth. Mandy then pulls herself and Urside to humanity's new life on 2036 Mars, where she not only realizes that Mars is her true home, but also that she's a reincarnation of an ancient Martian empress. -- publisher's website