H. Beam Piper
Ace Books 
Synopsis: The Federation has fallen, civilization collapsed and high technology is preserved on only a few worlds, among them the Sword Worlds, home of the Star Vikings, who prey on weaker worlds as their namesakes preyed on weaker communities in Europe. On one such Sword World, Gram, Lucas Trask, a noble, gets married. Less than an hour after his wedding to Elaine Karvall, Trask is badly wounded and his new wife is killed by Andray Dunnan, a mad would-be suitor of Elaine’s. Dunnan escapes immediate vengeance by fleeing Gram, stealing the starship Enterprise [no relation]. Trask, who up until now has seen the activities of the Star Vikings as draining the Sword Worlds of vital skilled labour, no longer cares about the larger picture and only wants revenge. He stakes his holding to pay for a new ship, the Nemesis and sets out to find and kill Dunnan.