Ilium by Dan Simmons

From the towering heights of Olympos Mons on Mars, the mighty Zeus and his immortal family of gods, goddesses, and demigods look down upon a momentous battle, observing - and often influencing - the legendary exploits of Paris, Achilles, Hector, Odysseus, and the clashing armies of Greece and Troy.

Thomas Hockenberry, former 21st-century professor and Iliad scholar, watches as well. It is Hockenberry's duty to observe and report on the Trojan War's progress to the so-called deities who saw fit to return him from the dead. But the muse he serves has a new assignment for the wary scholic, one dictated by Aphrodite herself.

With the help of 40th-century technology, Hockenberry is to infiltrate Olympos, spy on its divine inhabitants…and ultimately destroy Aphrodite's sister and rival, the goddess Pallas Athena. On an Earth profoundly changed since the departure of the Post-Humans centuries earlier, the great events on the bloody plains of Ilium serve as mere entertainment.

Its scenes of unrivaled heroics and unequaled carnage add excitement to human lives devoid of courage, strife, labor, and purpose. But this eloi-like existence is not enough for Harman, a man in the last year of his last 20. That rarest of post-postmodern men - an "adventurer" - he intends to explore far beyond the boundaries of his world before his allotted time expires, in search of a lost past, a devastating truth, and an escape from his own inevitable "final fax." Meanwhile, from the radiation-swept reaches of Jovian space, four sentient machines race to investigate - and, perhaps, terminate - the potentially catastrophic emissions of unexplained quantum-flux emanating from a mountaintop miles above the terraformed surface of Mars.