Originally published in three volumes, The Mechanoid Invasion consisted of three sci-fi RPGs: The Mechanoid Invasion, The Journey, and Homeworld. The first book had all the rules necessary for play. The second book, The Journey, had a summary of the rules, continued the plot, added rules for Magic(!), and added additional enemy statistics. The last book concluded the plot and again was self-contained. With all the rules for play, Homeworld also had additional player character races, and of course: more Mechanoids.