Primarily Abnett has worked for 2000 AD and Marvel Comics (including their UK imprint) since the early 1990s, although he has also contributed to DC Comics titles. His Warhammer Fantasy and Warhammer 40,000 novels and graphic novels for Games Workshop's Black Library now run to several dozen titles.
He has written novels set in the Warhammer 40,000 universe (Military science fiction genre). They include the Gaunt's Ghosts series, the Eisenhorn trilogy and Ravenor spin-off and more recently, the first book of the Horus Heresy series, the SF bestseller "Horus Rising". He has also written three Warhammer Fantasy novels. He also wrote a novel for the Doctor Who spin-off Torchwood called Border Princes in 2007.
In addition DnA have done a lot of work on Marvel's "cosmic" characters. They expanded on their work in Annihilation: Nova and Nova, and piloted the next big event Annihilation: Conquest. They said "we were approached by Andy Schmidt, who edited the first 'Annihilation' event, and asked to pilot the next event, which Bill Rosemann is editing." They ended up writing the Prologue, the Nova series crossover and the main Annihilation: Conquest limited series. The characters then became the core of a new Guardians of the Galaxy.
It was announced at Wizard World Chicago in June 2008, that Abnett and Lanning had signed an exclusive deal with Marvel, which they hope will give them time to work on the "cosmic" characters they have been dealing with, as well as more earth-based ones. The contract allows them to finish existing commitments, so they will be able to finish their fifteen issue run on The Authority. In addition Marvel has allowed the contract to include "a couple of exceptions that are not direct competition, for example, Dan's 2000AD work in the UK and his GamesWorkshop novels. The first major work to emerge after this deal will be War of Kings, a crossover storyline, emerging from Secret Invasion, that will pitch Black Bolt (and the Inhumans) against Gabriel Summers (and the Shi’ar Empire) but will also draw in other teams and characters, including Nova, the Guardians of the Galaxy and the Starjammers.