Abaddon's Gate
Abaddon's Gate is a science fiction novel by James S. A. Corey (pen name of Daniel Abraham and Ty Franck). It is about a conflict in the Solar System that involves the polities of Earth, Mars, the Asteroid Belt and the outer planets, and a mysterious self-replicating alien technology (a von Neumann probe) of immense power. It is the third title of The Expanse series and is preceded by Leviathan Wakes and Caliban's War. The series is continued in Cibola Burn. The book was released on 4 June 2013, as well released as an audiobook by Audible, narrated by Jefferson Mays.

Abaddon's Gate was adapted into episodes 7 to 13 of the third season of the television series The Expanse in 2018, with its title taken for the final episode of that season. It was the last book in the series to be adapted before the show's move from Syfy to Amazon Prime.

Plot summary
Six months have passed since the Protomolecule created a structure on Venus and left the planet. It stops two AU beyond the orbit of Uranus and proceeds to build a gate, a wormhole, which is referred to as "The Ring". The UN, Mars and the Belt sent ships to keep an eye on it. 

Holden, Alex, Amos and Naomi are taking a vacation on Ceres, having made good money using the Rocinante as freelance courier and escort ship. UN Public Broadcasting contacts Holden, wanting to make a documentary about Holden and the Ring. Holden initially refuses, even though the vision of Miller, which has appeared to Holden occasionally since the Protomolecule crashed on Venus, has been urging him repeatedly to go to the Ring. However, the Martians threaten to take back the Rocinante, and Holden makes a deal with UN Public Broadcasting to do the documentary in exchange for them paying off the Martians.

Clarissa Mao, sister of Julie Mao, plots revenge against Holden, whom she believes caused the downfall of her father Jules-Pierre Mao, who was responsible for the research into the Protomolecule. 
She has black market implants installed, which can make her extremely strong on command, and gets a job under an assumed identity (Melba Koh) as an engineer on the Cerisier, a civilian support ship to the Thomas Prince, the UN exploratory ship heading for the Ring. 
When the Cerisier gets close to the Rocinante, Clarissa sends a code to the ship, which activates software secretly placed there by someone of the documentary crew at her instruction. The software takes control of the Rocinante, disables the communication system and controls the weapons, shooting down one of the other ships heading for the ring. A faked video message of Holden claiming responsibility for the attack is broadcast.

Amos discovers the planted software. Realizing it could only be planted by the documentary maker, Monica Stuart, or her cameraman Cohen, he forces a confession out of Cohen. Cohen doesn’t know Clarissa’s name, but draws her face. Holden, thinking it’s Julie Mao, assumes that this is another one of the Protomolecule’s ploys to manipulate him. 
The remaining exploratory ships, in retaliation to what they perceive as an unprovoked attack, start firing on the Rocinante. Holden sees no other option than to flee into the Ring.  Miller appears and warns him to slow down the ship as much as possible before entering the Ring.

Once inside the Ring, the crew tries to repair the communication system in order to contact the other ships and convince them of Holden’s innocence. In the meantime, they explore the inside of the Ring. Filmed by Monica, Holden talks about what they call "the slow zone", and something they decide to call the Ring Station, a "big silvery blue glowing ball" in the center of the area beyond the Ring. The maximum speed allowed in the Slow Zone appears to be 600 m/s. Objects travelling faster are grabbed by "some sort of field" and dragged to a "garbage ring" circling the Station. Holden decides to go to the Station, figuring this is what the Protomolecule wants him to do.

On his way to the Station, Naomi informs Holden that the other ships have come through the Ring as well. The Martians have launched a skiff in pursuit, but Holden will reach the Station before them. Approaching the Station, the surface opens, allowing Holden inside, then closes again. 
The vision of Miller guides Holden deeper and deeper into the Station, informing him after a while that the Martians have also entered. They catch up and attack Holden. The Station stops the bullets in "a diffuse cloud of gray". The Protomolecule constructions in the room then attack the Martians. One of the Martians gets ripped apart, the others retreat. Miller tells Holden the Station now considers the speed of a bullet a threat and will have adjusted the speed in the Slow Zone. 
Holden and Miller advance through the Station until they encounter "a massive octagonal construct of glowing blue metal". Miller urges Holden to touch it. Upon contact Holden experiences visions of the civilization that built the Protomolecule. They were attacked by an unknown entity. Trying to stop the attack, the Protomolecule destroyed thousands of galaxies. 
The Martians come back and arrest Holden. In his cell on the Hammurabi (the Martian exploratory ship) Miller advises Holden to get all the ships to turn off their reactor. This will show the Station that they are not a threat and hopefully convince it to release them from the Slow Zone. 

Because of the sudden change in the speed limit, all the ships near the ring abruptly and drastically slow down, causing the people inside to get tossed about. Casualties are high and wounded survivors get transported to the OPA ship Behemoth (previously the Nauvoo), where they can be most effectively treated. 

On the UN ship Thomas Prince, Clarissa is recognised by Tilly Fagan, an old family friend, just before she leaves for the Rocinante to destroy it. Tilly tells Anna, a pastor from Earth she met on the journey. Anna follows Clarissa to the Rocinante.
Aboard the Rocinante, Naomi discovers Clarissa and the two fight as Clarissa attempts to destroy the ship. Anna arrives just in time to stop her. Clarissa is heavily injured. They all transfer to the Behemoth in order to receive medical treatment.

Meanwhile on the Behemoth, Carlos “Bull” Baca, the ship’s Chief Security Officer, clashes with his Captain, Klaes Ashford, about critical decisions. Bull relieves Ashford of command, instating XO Michio Pa as captain. When Ashford is freed by a clergyman from Earth, father Cortez, they plan to destroy the Station and the Ring, including all the ships inside the Ring. Father Cortez frees Clarissa and they head to the command center.

Bull, Anna and the crew from the Rocinante go on the offense: Naomi will turn off the Behemoth’s reactor, Alex will return to the Rocinante to turn off theirs, Anna will try to convince the other ships to turn off their reactor. A brutal battle ensues as both sides attempt to prevent the other’s plan, which Ashford’s side is on the brink of winning. In a final desperate attempt, Anna convinces Clarissa to shut down the control system of the Behemoth. 

After all reactors are finally shut down, Miller appears to Holden and informs him that he has convinced the Station that the ships are not a threat. Furthermore, the Station opens more than a thousand new rings inside the space behind the Ring, each leading to a different solar system. Miller says the Protomolecule will never stop searching for its creators, even if they are long gone. As its instrument, Miller will keep using Holden for this search.

Anna convinces Holden to bring Clarissa to Luna to stand trial. In return, she will buy the Rocinante for him. Anna calls in a favour from Tilly, asking her (and her rich husband) to do so. 
The OPA leaves the Behemoth in the Ring as a waystation. The Martians also leave a ship behind to survey the gates.

Characters 

 James Holden, captain of the Rocinante, former UN Navy (UNN) officer; from Earth (an Earther). His associates on the Rocinante are pilot Alex Kamal, engineer Naomi Nagata and mechanic Amos Burton.

Joe Millers consciousness continues on in disembodied form, now part of the vast protomolecule matrix and used for his investigative capabilities. Talking to and trying to work with James Holden, he has limited insight into the actions taken by the gate, but knows there is a vast tapestry of opportunity and danger associated with it and those who built it, because someone destroyed them.

 Clarissa Mao, younger sister of Juliette "Julie" Andromeda Mao and daughter of Jules-Pierre Mao, who was president of the multi-planet corporation "Mao-Kwikowski Mercantile" also known as "Mao-Kwik". Jules-Pierre was part of various conspiring organisations, all of whom wanted to use the protomolecule for profit. 

 Carlos "Bull" de Baca is a former warfighter and friend to Fred Johnson. He's given the job of third in command of the Behemoth, formerly known as the Generation Ship Nauvoo, which the OPA salvaged and repurposed as a warship. 

 Klaes Ashford, captain on the Behemoth. 

 Michio Pa, XO on the Behemoth, "promoted" to captain after the coup.

 Annushka "Anna" Volovodov is a Methodist pastor from Europa who joined the expedition as part of a UN delegation of religious figures and artists selected to witness the start of a new epoch of human history. Her ship joins others following Rocinante into the gate, and she tries to pull fragile strings of common interest together against the gales of politics, self-interest, and madness driving others in the expedition.

 Monica Stuart works for UN Public Broadcasting. She and her cameraman Cohen go aboard the Rocinante to make a documentary about Holden and the Ring.

Reception
Abaddon's Gate won the 2014 Locus Award for Best Science Fiction Novel. Publishers Weekly gave Abaddon's Gate a starred review saying that "series fans will find this installment the best yet".

References

The Expanse
2013 American novels
Novels about extraterrestrial life
Fiction about main-belt asteroids
Novels set on Mars
Novels by James S. A. Corey
Fiction about the Solar System
Space opera novels
American science fiction novels
Orbit Books books