In television, he is known for co-creating the animated TV series Tripping the Rift,[2] producing the first season of Steven Universe, and acting as a co-showrunner on She-Ra and the Princesses of Power.

As the series initially reprinted material from the British anthology Warrior his work on the main strip started in Miracleman #6, cover dated February 1986.

Soon after being commissioned, he also began writing and illustrating the weekly maxi-series U.S. War Machine for then-recently launched Marvel MAX imprint.

[23][24] During this run, he showcased the beginning of the relationship between Cyclops and Emma Frost following the death of Jean Grey[25] and introduced new versions of the character Xorn[26] and the Brotherhood of Evil Mutants.

[29] In 2003, Austen wrote a brief run on Captain America, finishing the storylines that were started by the outgoing writer John Ney Rieber.

Agent and Namor the Sub-Mariner attempting to liberate a Middle Eastern country from its corrupt leadership, served as launching pad for the short-lived New Invaders series.

[32][33][34] Non-superhero Marvel work of the time includes The Call of Duty, a project consisting of several mini-series conceived in the aftermath of the September 11 attacks that were written primarily by Austen (with one series written by Bruce Jones) and featured firefighters and emergency service workers dealing with paranormal phenomena in the Marvel Universe,[35][36] as well as Eden's Trail with artist Steve Uy, a series in "Marvelscope" (landscape) format created to capitalize on the burgeoning manga market which resulted in controversy when Uy publicly disowned the project, calling it a "bad dream".

[37] Also in 2003, Austen returned to DC Comics with the limited series Superman: Metropolis which followed the life of Jimmy Olsen and other citizens of the eponymous fictional city.

[5][11] In 2004, Austen began self-publishing WorldWatch, a superhero series which he described as similar to Warren Ellis's The Authority with more explicit depictions of sex, violence and realpolitik.

In a subsequent interview, Austen revealed that this was intended as a joke (since he himself was the publisher and thus could not be fired from the book) and expressed disappointment in the fact that most readers had not understood it.

[5] In 2006, Austen wrote Boys of Summer, an English language adult-themed manga illustrated by Hiroki Otsuka and published by TokyoPop.

[43] In 2020, Austen returned to comics with Edgeworld, a five-part series with artist Pat Oliffe, published digitally via Comixology.

In Austen's point of view, there was a small group of people, not representative of the wider comics readership, that used internet message boards, blogs and newsgroups to attack him on a professional and personal level.

[45] Austen has expressed admiration towards such comic book creators as Brian Michael Bendis, Paul Jenkins, Bill Sienkiewicz, J. Michael Straczynski, Ron Garney, Bret Blevins, J. H. Williams III, Al Williamson, John Romita, Sr., Rumiko Takahashi, Katsuhiro Otomo and Mitsuru Adachi.