Celestial Mechanics #1

Space travel is a Halplex monopoly in the 27th century. But when Widget finds and repairs an old derelict starship, she discovers the secrets of the spacedrive and decides to go into business for herself. Terebinthia and her friends Shan and Flange are about to graduate from the Space Patrol Officer Training Academy on Luna City, when Flange's old boyfriend, Tristan Bok, shows up. He is an assassin for Halplex assigned to eliminate the hacker that has tapped into sensitive material about the spacedrive.