Ithaka Rising: Halcyone Space, book 2

A derelict ship and a splintered crew are not the rewards Ro had hoped for when she helped disrupt her father's plans to start a war with smuggled weapons. But with the responsibilities of full Commonwealth citizenship and limited resources, she is forced to take her father's place working as an engineer on Daedalus station while she and Barre try to repair their damaged freighter, Halcyone. Barre's brother, Jem, is struggling with the disabling effects of his head injury, unable to read or code. His only hope is to obtain a neural implant, but the specialists determine he is too young and his brain damage too extensive. When Jem disappears, his trail dead ends at the black market. Ro and Barre race to find Jem before he sells his future, risking his mind for an illegal neural implant. But they're not the only ones looking for "The Underworld" and its rogue planet, Ithaka. What they find endangers more than just the three of them and forces them to confront a very different truth about the war they believed was ancient history.