Confederación

William Mandela is a genetic throwback, one of the small group of humans who fought and survived the Forever War. They returned to find humanity has evolved into a group mind called Man. Surrounded by a society that is too autocratic and intrusive, living a dull existence which cannot compare to the certainties of combat and feeling increasingly alienated, the veterans plan an escape to the future by means of space travel and relativity. But when their ship starts to fail, their journey becomes a search for the Unknown, the elusive entity responsible.

Around 1991, Haldeman wrote: ""What is the book about? The subtitle A 'Short Comic Novel of Existential Terror' is accurate. In a way, it's a horror novel tinged with ghastly humor, as the apparently insane ghost of Ernest Hemingway murders a helpless scholar over and over; the scholar slipping from one universe to the next each time he dies, in what is apparently a rather unpleasant form of serial immortality. The tongue-in-cheek explanations for how this could happen qualify the book as a science fiction novel.
... It may be the most 'literary' of my books, but it also has the most explicit sex and the most gruesome violence I've ever written. Nobody will be bored by it."

In the 21st century, immortality via the complex operation known as the Stileman Process is attainable by a few wealthy and determined individuals, but the motivations that drive humans to live forever remain shrouded in mystery until "immortals" Dallas Barr and Maria Marconi stumble across a dangerous secret and find themselves fleeing for their lives--which have suddenly become very short.

2043 A.D.: The Ngumi War rages. A burned-out soldier and his scientist lover discover a secret that could put the universe back to square one. And it is not terrifying. It is tempting...

Joe Haldeman "has quietly become one of the most important science fiction writers of our time" (Rocky Mountain News). Now he delivers a provocative novel of a man who stumbles upon the discovery of a lifetime-or many lifetimes.

Grad-school dropout Matt Fuller is toiling as a lowly research assistant at MIT when, while measuring subtle quantum forces that relate to time changes in gravity and electromagnetic force, his calibrator turns into a time machine. With a dead-end job and a girlfriend who has left him for another man, Matt has nothing to lose taking a time machine trip himself-or so he thinks.