Furman's writing is notable for his use of pseudo-religion and lore as an underpinning theme to the Transformers mythology. He invented an origin story for the Transformers that involved an ancient struggle between the colossal godlike creator, Primus, and his counterpart, the colossal godlike destroyer, Unicron. The latter was borrowed from the Transformers movie, where he appeared with no given a backstory (an origin for Unicron later came in the third season of the original Transformers cartoon series). According to Furman's origin story, The Transformers were a creation of Primus as a warrior race who were to be the last line of defense against Unicron. This origin differs from the third season of the cartoon series, where the Transformers were originally created to be robot servants of the alien Quintessons, who often sold them to other races.

Aside from the creation myth, mythological underpinnings can be found in several of his stories such as the Matrix Quest storyline, where the Autobots and Decepticons search for the Creation Matrix, a powerful object constructed by Primus.

Furman's Transformer: Generation 2 plot-line in 1993 introduced the characters Jhiaxus and Liege Maximo, one of the first Transformers. Liege Maximo had killed the first Prime in order to steal the Matrix and claimed that the Decepticons descended from him. Since Transformers Generation 2 was canceled after 12 issues, the Liege Maximo storyline was concluded in the convention exclusive novella Alignment.

Over ten years later, Furman was brought in by the now-defunct independent comics publisher Dreamwave to write some of its Transformers comics, including "The War Within", a six issue prequel set on Cybertron before the Autobots and Decepticons took their battle to Earth. It spawned two sequels - "TWW: The Dark Ages" and "TWW: The Age Of Wrath" (uncompleted). His work on the Armada and Energon titles were also received better than the anime series from which they were based on. Furman was to have continued on with Dreamwave, but its contentious closure resulted in the premature end of the Energon and The War Within titles.

Furman's convention exclusive novella/comic serial, The Omega Point, includes an apocalyptic End of Days scenario for the Transformers, and a quest by one of the heroes to ask for help in the land of the dead.

Simon Furman still collaborates with regular Marvel UK Transformers artist, Andrew Wildman, as WildFur Productions. Their most recent collaboration was on the Macromedia Flash online, interactive comic Industrial Strength; which they produced with UK New Media expert Adam Jennings.

Away from Transformers, Furman wrote a Doctor Who audio adventure for Big Finish. The Axis of Insanity features the Fifth Doctor, and was published in 2004. He also contributed a number of stories starring Judge Dredd to the DC title Judge Dredd: Lawman of the Future, as well as one-off stories to Dredd's home title 2000 AD.

Furman is currently writing a new continuity of "Generation 1" Transformers comic books for IDW Publishing. Furman likes to tell his stories realistically with maps helping out his locations. Furman often focuses his stories on responsibility.

Recently, Furman wrote the Annihilation: Ronan mini-series for Marvel Comics, a series focusing on the character Ronan the Accuser that ties in to the Annihilation crossover.

His series Infinity started publication in June 2007, based on Dynamite Entertainment's Terminator 2 license and he has produced a sequel, Revolution. In the United Kingdom, has been doing original strips for Titan Magazines' upcoming Transformers title., as well as contributing to the strips for Titan's Torchwood magazine. He is also writing a Maximum Dinobots mini-series.

Comics work includes:

• Scream! #3 (1984)
• The Transformers #13-21, 29-32, 45-50, 59-65, 74-88, 96-104, 113-120, 125, 130-138, 146-153, 160-161, 164-173, 182-189, 198-205, 213-332
• Doctor Who Magazine #111-113, 117, 130-135, 140
• ThunderCats #10, 30-35
• Action Force (UK) #1, 2, 8, 14-17, 24-27, 47-50
• Action Force Monthly #2-6, 8-10, 14
• Dragon's Claws #1-10
• Death's Head #1-7, 9, 10,
• Death Metal #1-4
• The Transformers #56-80
• Brute Force#1-4
• Robocop #12-23
• Sensational She-Hulk #24-27
• Alpha Flight #110-112,114-130
• What If...? Vol.3 #51,53,54,59,64-66,72,74,76
• Generation 2 #1-12
• Northstar #1-4
• The War Within vol.1 #1-6,vol.2 #1-6,vol.3 #1-3
• Armada #6-18
• Energon #19-30
• DOLL (English translation)
• Necrowar #1-3
• Transformers Summer Special Energon story
• Infiltration #0-6
• Stormbringer #1-4
• The Gathering #1-4
• Spotlight vol.1 #1-5, vol.2 #1,3,4, vol.3 #1,2,4,5
• Amazing Fantasy # 16-20
• Toxic Crusaders #1
• Jetix Magazine (Writer for the Power Rangers SPD comic strip)
• Escalation #1-6
• Movie Prequel #1-4 (with Chris Ryall)
• Infinity #1-5
• Transformers UK Magazine #1-current
• Devastation #1-6
• The Ascending #1-4
• Sourcebook #1-4 (with Ben Yee)
• Annihilation: Ronan (4-issue mini-series, Marvel Comics, 2005)
• Revelation #1-4