What is the Fall of Reach novel plot?
Here’s a summary. In short, the humans and the Master Chief fight against the alien Covenant forces until they eventually end up at the Halo as found in Combat Evolved.
Or a longer version!
The Fall of Reach novel, written by Eric Nylund, opens with the civilian Dr. Catherine Halsey and Lieutenant Jacob Keyes traveling to meet John, a six-year-old boy. Dr. Halsey reveals to Keyes that John is one of 150 children who possess rare genetic markers making them suitable for conscription into the SPARTAN-II program, a secret experiment with the aim of creating super soldiers for the UNSC to quell rebellions.
Seventy-five of the children are kidnapped by agents of the Office of Naval Intelligence (ONI) and replaced by clones engineered to die of natural causes shortly after so no one around the children are suspicious in the future. From this point on, the recruits are known only by their first name and a three digit number. John-117 and the rest of the children are drilled and trained by Franklin Mendez and John demonstrates leadership of his fellow Spartans leading to his promotion to squad leader.
In 2525, the Spartans undergo a series of surgical enhancements which turn them into highly efficient super soldiers at the cost of crippling or killing more than half of the original seventy-five. The Spartans are also equipped with powerful MJOLNIR battle armor, designed to respond as quickly as the soldier’s thoughts. John-117 is given the rank of Master Chief Petty Officer.
The Spartans are highly successful, but they experience a mission priority shift after a collective of alien races known as the Covenant begin obliterating human colonies, declaring humanity’s destruction as the “Will of the Gods”. Mendez leaves the group to train the next generation of Spartans as John and his comrades first face the Covenant.
By 2552, the war against the Covenant is going dreadfully. The technological superiority of the Covenant means that space battles heavily favor the Covenant, and the UNSC can only win engagements by suffering tremendous losses. To prevent the discovery of Earth or other human colonies, Vice Admiral Cole creates the “Cole Protocol“, which forbids direct slipspace jumps to planet Earth or any other large population location and mandates the destruction of a ship before it can be captured by the Covenant.
Jacob Keyes, now commander of the destroyer Iroquois, discovers four Covenant ships arriving at the Sigma Octanus System, and single-handedly destroys three of them; his heroics earn Keyes the rank of Captain. The Covenant conspire to overrun Sigma Octanus IV, searching for a mysterious ancient artifact. Despite an expensive and exhausting fight, the human forces manage to repel the Covenant, and Keyes intercepts a coded Covenant transmission from the surface before the Covenant retreat. The Iroquois heads to Reach, unwittingly bringing a Covenant tracking device with it.
Soon after, Keyes is given the command of the UNSC cruiser Pillar of Autumn for a secret mission; the Spartans are to capture one of the Covenant’s religious leaders, a Prophet, and barter a truce. Dr. Halsey also introduces John to the artificial intelligence Cortana, who would assist the Spartans by residing in their MJOLNIR armor. Before the mission can begin, however, Reach is attacked by a massive Covenant fleet.
John 117 and Cortana reach the Pillar of Autumn, but most of the other Spartans are presumed killed as the Covenant vitrify the surface of Reach, turning the landmasses into glass.
Cortana initiates a slipspace course based on the ancient glyphs intercepted by the Covenant at Sigma Octanus, the course takes them to a massive ringworld known as Halo, setting the stage for the events of the Xbox game, Halo: Combat Evolved
Source: Amended from Wikipedia