Dirge by Alan Dean Foster (American, 2000)

Summary:
This story presents the events of a war in the eyes of different characters.
  
  The general story is that humanity discovers a planer called Argus V, or Treetrunk. When humans go to colonize that planet, they meet a race called the Pitar. The Pitar are the closest species to human beings that humanity has ever encountered: They are almost phisically perfect, and have a wider variety of hair and eye colors. Additionally, the Pitar are friendly towards humans, saying they want to observe and learn from them, so humans take the Pitar to earth. 
  
  On the other hand, an insectoid species called "Thranx", who lived on earth, wants to form a close alliance with the humans. Since some xenophobe humans regard the Thranx as abominations, they invade a Thranx colony in the Amazons and cause a genocide, which creates a very big conflict between humans and Thranx, but also is the origin of a new religion: The United Church. Still, the Thranx are worried because their relations with humans are not good anymore, especially since the Pitar came into the scene. 
  The colony in treetrunk begins to grow, with almost 600,000 humans in the planet. 4 Years after the beginning of the colonization, news come that the colony in Argus V has been killed by unknown attackers, and when investigating, humans find Allwyn Mallory, the only survivor of the massacre. He says that the Pitar were the ones who killed humans, but no one believes him. It is until he provides evidence that people believe him, and signal the Pitar as the perpetrators of the attack: they killed humans and stole the female reproductive organs from the victims. The Pitar first deny the accusations, but then most of them flee the planet, fight or kill themselves.
  
  When humans prepare for war against the Pitar, the other species in the area stay out of the conflict, hoping that the humans and the Pitar kill each other. The Thranx debate whether they should help the humans or not.However, when war finally comes, humanity's armed forces are not enough to fight against the Pitar's defenses. After a year of war, the Thranx finally offer to help the humans. After two more years of war, Thranx and Human scientist find that both species complement each other and form a new weapon, which finally allows the invasion of the Pitar. 
  
  However, the Pitar show to be very arrogant and refuse to surrender. They prefer to die, which causes the extinction of the Pitar. Scientist research the Pitar after the war, and find that they are extreme xenophobes that wanted to steal human technology to exterminate humans, Thranx and other species, because they saw them as inferior and undeserving of life. The big problem, was that the Pitar females only ovulated once a year, so they had very few kids. To overcome this problem, they stole the sexual organs of the human females to create Pitar fetuses and increase their population and give them opportunity to fulfill their plan.

Another summary:
Amid the strengthening of diplomatic relations between the human race and the Thranx, an alien race that was found in the Reserva Amazonia, humanity now faces the discovery of a planet called Argus V; Alwyn Mallory, a member of the survey mission's support team, is in charge of exploring this place.
 In addition, a different alien race called the Pitar is discovered. Nonetheless, it is the Pitar that initiate the contact with the human race and offer to establish relations, so it could be said that humans are the discovered species. This recently-found race does not look at all like the Thranx, at least in the physical aspect. Unlike the latter, the Pitar are described as "gorgeous" and "beautiful"; since they are a kind of humanoids, they dazzle human beings with their superior beauty. It is precisely this physical difference between the Pitar and the Thranx--who have an unpleasant aspect of insects--what shakes the close relationship that has been developing for years between the Thranx and human beings. Humans get carried away by appearances and by the fascinating aspect of the Pitar to such an extent that issues related to the Thranx go completely unnoticed by the media, even when the colony of the Amazonia is attacked and a large amount of Thranx is murdered. This attack, however, leads to the founding of the United Church between two religious members of both races. Time passes and not much is revealed about the Pitar; but the human race remains so captivated by them that they do not suspect that this race has bad intentions at all. Suddenly, a tragic event occurs: thousands of humans are cruelly and mysteriously murdered in the colony established in Argus V. There seems to be no way to discover the responsible of the massacre until the only survivor of the attack is found: Mallory, who points to the Pitar as the cause of the terrible genocide against humans and has a video recording as proof of his claim. The Pitar have no way of denying their guilt in the face of such evidence, so the ones on Earth try to escape from being arrested by humans, and their confrontation with them ends in the death of several of the attackers. Humans, on the one hand, resolve upon initiating a war against the Pitar, which results in the total destruction of the latter. On the other hand, victory over the Pitar is not easy: humans do not expect to face this race's technological development, which has been perfected to defend them efficiently from attacks. With great difficulty, and with the aid of Thranx force and intelligence, humans advance toward the Pitar fortress. The Thranx manage to design a functional weapon to attack Pitar warships. Although the creation of this weapon is what finally annihilates the Pitar, they do not surrender easily and fight until every one of them is killed. After this conflict, it is discovered that the thought of the Pitar was governed by their xenophobia and their plans to destroy the other especies. It is also discovered that their plans were partially frustrated because they did not have enough lineage to carry out a successful destruction. So, during the attack on the human colony on Argus V, they modified human embryos to create more Pitar offspring. If had they not been discovered, they would probably have fulfilled their mission to exterminate human beings and the other races.

Another summary:
The future has come and not only have humans colonized numerous planets, but they have also encountered various intelligent species of aliens along the way. Life on Earth is peaceful, as the planet expands its territory across the universe. The book begins with a group of humans who are investigating a world in hopes of colonizing it. As they go around the uninhabited planet, a ship lands with a life form which they had not encountered before. After some months Earth is ready to receive their explorers with the new alien form known as the Pitar. These happen to be humanoids that, according to earthly standards, are extremely beautiful; therefore, humans are more than glad to welcome them. This sits oddly with the Thranx, a bug-looking race of aliens that have been in good terms with humans for almost fifty years. The Thranx are not as easily swayed by appearances and resent the way humans set the advancement of their relations aside to concentrate on the Pitar. This new species is characterized by their shyness, as they do not share much about themselves or their planet. They are always cordial and quite graceful in everything they do. After a while of fraternizing with them, a meeting is called upon to decide who will get to colonize the planet where they made their first contact, now known as Treetrunk. The Pitar are not a colonizing race like humans or the Thranx and, therefore, have no use for the planet, which is why they grant humans the freedom to do with it whatever they want. Humans go ahead and start colonizing the planet, after a few years they have a fully functional community that can sustain itself. The Thranx and the Pitar alike enjoy visiting said colony, even if the weather is not suitable for either. Four years later, a cargo ship arrives in the colony to find it destroyed, every single human inhabitant has been killed. Nobody knows why. Helped by the Thranx, humans search for an answer, but nobody is able to provide one, there are no records of any type left. It is not until much later that a less technologically advanced, but highly thorough, race of aliens are doing some research around the devastated planet that they discover a single ship with a man on the verge of madness. The man, later identified as Alwyn Mallory, is taken to earth in total secrecy and kept in a secluded hospital until he wakes up. When he does, he tells the story of what really happened in Treetrunk. According to Alwyn it was the Pitar who not only killed everyone in the planet but also extracted the uteruses of women. Everyone finds this story so hard to believe that a Pitar is even sent to talk to him to no avail. That is when Mallory remembers he recorded a video through a remote media droid. The device with the hours of video is hidden in the moon of Treetrunk around which he was found. A whole fleet is sent there and, after losing almost all hope, they finally find the device with the incriminatory evidence. Humans declare war on the Pitar, who not only deny everything but hide away in their planet. The war is tough and humans do not seem to be able to win it; the Pitar have too strong a defense system. Eventually, the Thranx, seeking to improve their relationship with humans, offer their help. Warships are sent but also minds are brought together to create a weapon that can destroy the Pitar stronghold. The weapon they come up with is both sneaky and strong enough to get past the defenses, which allows the military a way of examining the Pitarian twin home worlds. Although the intent was not to commit a genocide, the Pitar seem to leave them no other choice. The outcome is not good for the Pitar, leaving three devastated planets, the Pitar homeworlds and Treetrunk.

World view: Describes in a variety of aspects and with some consistency an imaginary state or society which is regarded as better, in some respects at least, than the one in which its author lives.
Future projections: It’s a negative emotional reaction against technological (transcendental, evolutive) or social progress. As such, It shows the horrible consequences of utopia or at least portrays skepticism or disappointment in regard to scientific or technological miracles.
Ideology: The control or suppression of futuristic technology is used as a means to maintain dominance and stability.
Characters, plot and writing style: Black humor and satire are employed to expose, criticize or shame individuals or the society itself into improvement.
Classification: Dystopia