Battleship Destroyer

Jack should have died at Birth when his family's transport the Turner Joy was stranded in a deadly Neutron Star system. Certainly before he reached the age of 6, as his busy Trampship officer family simply waited for him to (pass on). Mostly ignoring Jack while leaving him to study under his grandfather's tutelage (an old Collage professor running from something) and playing The Battleship sim game. That is except for an abusive older brother. Then at 18, after a few too many drinks to celebrate, he was scooped up by the Republic Navy that had not seen a war in generations. A Navy desperate for experienced spacemen to man their new battleships in a losing war few people even knew about, yet.

Jack is put into a position to get a close look at the enemy and realizes that the Battleship fleet he is a part of is about to be trapped and destroyed. But he now knows what drives their ships and powers their weapons. That with equal or even better ships and weapons, he now knows how to build, they could win the war and humanity could survive. If he can survive long enough to.

Thus starts a desperate journey to survive incredible odds long enough to develop or steal the enemies technology. Then test and manufacture the equipment and fleets to defeat an enemy that is only known as Spiders because of the shape of their ships. The only other thing known about them for sure in the beginning other than that they were slaughtering any human ship and enslaving and stripping every system and planet they came across, ignoring all attempts to negotiate.