Space Viking by H. Beam Piper (American, 1983)

Summary:
Everything begins in the colonized and highly technological planet Excalibur, characterized by space travel and continuous interplanetary wars. On the day of the wedding of the Baron of Traskon, Lucas Trask, and Elaine Karvall, celebrated on Gram. Andray Dunnan, a man obsessed with Elaine, interrupts the event and makes a scandal arguing that their marriage is for convenience and that the one Elaine really loves is him, although this only comes from his imagination. When Lord Lucas Trask is about to take his wife to their new married house, Dunnan arrives, murders Elaine with six shots and leaves Trask and Elaine's father injured, then escapes in one of Duke Angus’ spaceships.
 When Trask wakes up he finds out everything that happened and is destroyed when he learns that Elaine has died. After little time of recovery he decides that he is going to look for the fugitive Dunnan by himself, which is why he offers Duke Angus to give him his title of Baron of Traskon in exchange for a ship, the Nemesis, just like the one Dunnan took, to become a Space Viking and find Dunnan; more than one person warns him of how difficult it will be to find him through space. He asks Otto Harkaman to accompany him in his search and command his ship; Otto accepts despite the difficulty that it entails.
 
 The first place they arrive at is a primitive planet called Tanith, in which Trask decides to develop, in association with the crews of the Space Viking ships Lamia and Space Scourge, a base raiding according to the plans that Duke Angus had previously made. For this, Trask begins to give technological training to the inhabitants of the planet. After beginning with their plans, the first planets they attack are Khepera, Amaterasu, and Beowulf, from where they collect a large boot which they send directly to Gram, where the magnitude of the collection causes great interest and makes many men begin to migrate from Gram to the kingdom that is being built under the command of Trask. Meanwhile, Duke Angus manages to seize Gram, proclaims himself king and gives Trask the title of prince and his viceroy in Tanith.
 
 After making an investigation about the resources available in the conquered planets, Trask starts a sustainable trading system among them. He begins to hear from Dunnan and rumors that he has been close and that he has even attacked Mardukan colonies. When he visits the third colony, he has a confrontation with Dunnan's ships and manages to destroy two of them, but misses on Dunnan’s whereabouts.
 
 Trask returns to Marduk with his troops and develops a close relationship with King Mykhail and the royal family, in addition to having a romantic interest in Lady Valerie, a Mardukan woman. After realizing the abuses committed by King Angus in Gram, Trask decides to declare Tanith independent and disclaims any relationship with the Duke. Not long after that, a war breaks out on Gram, which leads this and other warring worlds to a rather regrettable situation, contrary to Tanith, which is quite harmonious and constantly growing.
 After a war led by Dunnan himself breaks out in Marduk, Trask gathers a fleet of ships, among which there are ships not only from Tanith and Marduk, but also several Space Viking ships alien to those kingdoms. They fight a battle to the death against Dunnan's troops and end up winning it. When Trask comes face to face with Dunnan after he is betrayed by his followers, he shoots him and ends his life. In the end Trask decides to marry Lady Valerie and obtains the title of king of Tanith, after which he proposes to establish fraternal and stable relations between the civilizations that surround Tanith.

Another summary:
The refugees from "The Big War" of the Terran Federation colonized a couple of planets which they named "The Sword worlds", which were politically organized on a system of kingdoms and duchies. The Big War also affected several planets causing inhabitants decivilization and regression to a semi-barbarism stage. Space Vikings took advantage of the situation and began to plunder this defenseless planets. 
 Lucas Trask, Baron of Traskon is about to marry Lady Elaine Karvall. But Andray Dunnan, nephew of Duke Angus of Wardshaven, is obsessively in love with Elaine, so he bounce into the wedding to claim her love. When she tries to explain to him that she is in love with Lucas, his anger boils over. He crashes the wedding ceremony with a machine gun, kills Elaine and steals the Duke's newly built starship, the Enterprise. 
 Lucas pledges the Barony of Traskon to Duke Angus in return of another warship. Even though he didn't agreed with Space Viking's actions, he decides to be one just for taking revenge of Dunnan. He hires Otto Harkaman, an experienced Space Viking capitain and go hunting Andray Dunnan, no matter how small the chances of finding him are.
 Lucas Trask first visits Tanith, a primitive plantet and establishes a base there. The natives begin receiving a better treatment and training in technology. Duke Angus gains supporters on Gram and promotes himself to King and Lucas to prince.
 Prince Lucas Trask visits Marduk, a democratic and advanced planet, after finding out that Dunnan recently attacked there. He becomes friends with the Mardukan royal family, particularly KIng Mykhail and also pursues a romance with Lady Valerie, a mardukan noblewoman who is the lady-in-waiting of King Mykhails eight years old grand-daughter. 
 On Gram, King Angus starts abusing his power so Prince Trask declares Tanith's independence and renounces his fealty to Angus. Tanith becomes the future of the possible civilization reform while Gram, along other Sword Worlds are in decline.
 Lucas gets Dunnan and kills him as a less important event, at this point, he considers dealing with Dunnan less important than building a civilization on Tanith. Finally he decides to marry Lady Valerie and to form a League of Civilized Worlds.

Another summary:
Lucas Trask, Baron of Traskon, is about to marry the love of his life Elaine Karvall. This marriage will not only make him happy but also greatly benefit him as she is the daughter of a very important businessman. Then there is Andre Dunnan. He is said to be mad and has built in his head the delusion that Elaine is being forced to marry and that she actually loves him. This is, of course, not true and when he crashes the wedding party to take Elaine with him she tells him so. He is completely enraged by this and after the wedding ceremony he plots an attack on the couple. He shoots Lucas and Elaine and takes the Enterprise, a ship that was built and stocked by Duke Angus of Wardshaven for interplanetary exploration. Andre disappears into the vast universe. After being in and out of consciousness for many days Lucas is finally well enough to learn that Elaine was killed by Andre during the attack. He goes mad with rage and decides to leave everything behind to become a space Viking whose sole purpose is to hunt down and kill this man. He gives his Barony to Duke Angus (who is currently trying to become King of Gram, the planet they live in) in exchange for a ship, the twin to the Enterprise, which he calls the Nemesis. Duke Angus agrees, as having that Barony will help greatly in his endeavor towards kingship. Seeing how it will be nearly impossible to follow Andre across something as vast as the universe he decides to go to Tanith. This is a planet that was once colonized but after a huge interplanetary war among the Federation planets it has fallen back into barbarism. This is the planet that Duke Angus originally wanted to go to with the Enterprise to build a shipyard and a trade point. The objective is to wait for Andre to eventually show himself there. As the Nemesis arrives on Tanith they discover that two third-rate space Viking ships are already there waiting for them in hopes of getting something in exchange for releasing the planet. Lucas Trask is not interested in fighting these men but comes to an agreement because, even if they are third-rate, he could use two more ships to increase his fleet. With these two new captains they start doing their space Viking work, which is raiding planets. They raid a low-level planet first, followed by a mid-level and finally a highly civilized planet. All their raids are successful, if not easily. After this they realize that the last two planets, Amaterasu and Beowulf respectively, each have essential elements that the other doesn’t. Amaterasu has gadolinium, a chemical that is basic for space travel, and Beowulf has plutonium. Lucas begins a trade arrangement in which he buys gadolinium from one and sells it way higher to the other and the same with plutonium. This way he forms a sort of alliance and a steady income. This helps Lucas raise Tanith from a semi-barbaric planet to a full fledged civilized one where ships can come in an out with goods and information. Parallelly Duke Angus has now become King Angus and although at first he seems to be quite the same, as time goes by his messages get more and more arrogant. Lucas has had enough of King Angus’ madness and although he doesn’t officially declare himself King of Tanith he also doesn’t acknowledge Angus as having any kind of power over him or his planet. A few royals flee to Tanith to join Lucas who has been gathering information on Andre. The more he gathers the more it seems that he is planning to fight with Marduk, a highly civilized and powerful planet. In a planet that is allied with Marduk Lucas encounters the Enterprise in a fight with a Mardukan ship. He decides to enter the fight and help the Mardukans destroy Andre’s ship. Lucas knew though that Andre was not in the ship, he must have been somewhere else, safe, in a planet. Afterwards Lucas goes to Marduk himself and befriends the royal family. In the planet there seems to be some dissent arising. A new party has started to form that seems to follow patterns similar to the Nazi party back when humans only lived on Terra. There is talk of getting rid of a particular group of citizens and Lucas identifies this as a potential problem. He warns the royal family about the man leading the political party, but their hands are tied as they blindly believe in the government they are a part of. In the end this man, who was thought to lose popularity, is voted as new prime minister. This causes a revolution as he enters with armed men (weapons were not previously available for anybody) and tried to take complete control of the world. The old king is being used as a puppet and the rest of the royal family flees to Tanith seeking Lucas’ protection. Meanwhile Lucas has to find a way to keep the Gram royals who have fled to Tanith united as they seem to be quite dispersed and this could cause trouble. He claims that Andre is the man behind all the unrest in Marduk and gathers a fleet to go with him to fight in Marduk. Upon arrival they learn that that is indeed the case, Andre is behind the party that has taken over the planet. After a battle Andre’s men are taken down and he is killed. Now, after so many years, Lucas can finally have some peace.

World view: The world portrayed in the story is an hypothetical society which seems to be worse than the one the author lives in.
Future projections: It’s a fearful prediction of the possible outcomes of today’s actions. Thus, it warns us against the terrible disasters (e.g. overpopulation, war, climate change) which would follow if there is no change in direction.
Ideology: The control or suppression of futuristic technology is used as a means to maintain dominance and stability.
Characters, plot and writing style: The story features a rebellion against the adverse circumstances (revolutionaries may exploit newer technologies for these ends).
Classification: Non-dystopia