The manual is divided into two sections, the first of which discusses the Colonial Marines and their structure, equipment and armaments, often accompanied by quotes from various Colonial Marine personnel. The manual describes the equipment of the Colonial Marines in great detail, and contains expansive descriptions of the M41A Pulse Rifle, the UD-4L Cheyenne Dropship and the Conestoga-class transport starship (such as the USS Sulaco). While staying faithful to the film, the manual also expands upon a number of topics not depicted in the film, including the heavy weaponry, artillery and armor support available to the USCM.
The first section also includes a brief history of human, colonial and military developments of the 22nd century, which subsequently serves as one of the most in-depth sources of information on the Aliens universe and its history up to the point of the Alien film series. The manual contains information about the organisation of the Colonial Marines, again staying faithful to the films while adding and expanding information.
The second section of the manual consists of a series of message transcripts between Weyland-Yutani Corporation personnel regarding the events of Alien and Aliens, interspersed with technical information on some of the non-USCM equipment mentioned, including the USCSS Nostromo and the Caterpillar P-5000 Work Loader. In particular, the Weyland-Yutani transcripts discuss theories on Xenomorph biology and how the species may be exploited for monetary and military gain. Presented in chronological order, these transcripts end with a Weyland-Yutani team rediscovering the Derelict Ship on LV-426, with the final entry being a communiqué from a science team preparing to enter the vessel to investigate.
The Colonial Marines Technical Manual had its origins in the pages of the Technical Readout section of the UK Aliens magazine produced by Dark Horse Comics in the 1990s. The section was written and illustrated by Brimmicombe-Wood. His business partner and future editor of the manual, David Hughes, was the magazine's other regular contributor of articles and reviews.
Numerous photos and illustrations for the manual were produced with use of actual movie props from the film's armorers, and from the licensed Alien War live-action ride in London at the time. For the photographic images included in the manual, the props were modelled by one of the actors who portrayed a Marine at the Alien War attraction. Other material was provided by 20th Century Fox, including illustrations by Aliens production designer Syd Mead.
20th Century Fox asked that the book focus on only the second film in the franchise, but since Aliens refers heavily to the first film, they allowed background information regarding the plot of Alien to be included as well. Material dealing with the third and then-unproduced fourth films was left out, with the exception of a brief reference to the damaged Bishop 341-B's remains being recovered following the events of Alien3.
- The Colonial Marines Technical Manual notably contradicts dialogue in Alien Resurrection that states Ellen Ripley's actions in Aliens and Alien3 effectively wiped out the Xenomorph species (at least to mankind's knowledge); the book briefly states that the Derelict Ship on LV-426 survived the explosion at the end of Aliens, and that it is subsequently rediscovered by Weyland-Yutani.