_Expendable_ by James Alan Gardner has an unusual premise. In the twenty-fifth century life is fantastic, people just about live forever thanks to YouthBoost and with advanced medical technology and quick responses, just about no one ever dies (at least violently).
Except for members of the Explorer Corps.
In a perfect world of perfect people, some just don't fit. They have some deformity, maybe a malformed hand or arm, a bizarre and startling facial birthmark, some sort of birth defect involving their ear lobes or hair. With most people in the Technocracy, these problems are usually fixed but for a small portion of the population, these defects are seen to have national security benefits. If the defect is not debilitating or life threatening (merely mildly inconvenient or just unsightly), if the person is otherwise capable and intelligent, efforts on the part of that person to have that defect surgically altered are quietly blocked behind the scenes. That person is groomed for the only position that is open to them, the Explorer Corps.
The powers that be, the admirals of the Fleet, concluded long ago that the loss of a crewmember was devastating to the ship's personnel, as it required days if not weeks of mourning, loss of readiness, and generally made for an unwanted distraction. However, if the person killed was one people were uncomfortable around, who was a social outcast, who while not hated was maybe pitted instead, well, it was too bad if that person was lost in the line of duty exploring some hostile alien planet, but the crew would say a few words, have a short memorial service, and then be talking about what was for dinner afterwards.
The Explorer Corps, while highly trained, very capable and intelligent individuals, were made of just these misfits. Though officially highly valued (the chief protagonist in the book, Explorer First Class Festina Ramos, is on the books second in command only to the captain of the vessel she served on, the _Jacaranda_), they were pretty much social outcasts, often making other members of the fleet uncomfortable, usually clinging together with other explorers or eating alone in their rooms. The Explorers well knew not only their social position in the scheme of things but also how the Fleet ultimately saw them. Their name for themselves was ECM, standing for Expendable Crew Member. Their job was to explore alien planets, relaying what they saw back to the vessel. While many worlds turned out to be safe or even boring places to explore, a great many explorers have lost their lives, going "oh sh**!" as the Explorers say among themselves, an acknowledgment of common last recorded words of many an Explorer as they met their demise.
Festina Ramos and her partner, Yarrun Derigha, had done pretty well as Explorers -i.e. not having been killed in the line of duty - but one day an apparently very unstable Admiral Chee is escorted aboard with sealed orders, orders for the two them to accompany the admiral to the planet Melaquin, the "Planet of No Return," a graveyard for dozens of Explorers, most of whom died in ten minutes or less on the planet for reasons unknown. Though the planet looked very Earth-like to automated probes sent before each Explorer expedition, something on the planet killed people off in minutes. Was it disease, hostile aliens, some bizarre and undetected weather phenomenon? No one knew, but Festina knew she and Yarrun were going there.
Oh, and they aren't allowed anything more powerful than a stun gun. See, in this setting the League of Peoples is the ultimate big brother. A diverse and for all practical purposes omnipresent and omniscient organization made up of not only "normal" corporeal sentient races like humans but also of many powerful energy beings, the League monitors all space flights. While weapons are allowed on a race's homeworld, they are not allowed to leave the atmosphere of that world. Further, those who have committed murder, ordered deaths, allowed murder to be committed, or knowingly aided murderers (what the League calls "unsentient acts") are stopped cold. Depending on the situation, the League's instant reactions can vary from stopping the heart of a murderer to destroying outright an entire ship.
I won't say anything more about the book, but it was well-written and a fast read. The big secret of Melanquin was interesting and tied in well with the League, the Explorer Corps, and secrets held by the highest levels of the Technocracy. An enjoyable book, it reminded me in some ways of some of the Golden Age of science fiction novels with it sense of wonder and wide-open possibilities. I have since read the sequels to the series and enjoyed them all, highly recommending the entire saga.