M. John Harrison 
Centauri Device [EPUB ebook] 

John Truck was to outward appearances just another lowlife spaceship captain. But he was also the last of the Centaurans, or at least half of him was, which meant that he was the only person who could operate the Centauri Device, a sentient bomb which might hold the key to settling a vicious space war. M. John Harrison’s classic novel turns the conventions of space opera on their head, and is written with the precision and brilliance for which is famed.