Is the only way to get the base game to shell out fifty bucks for a used copy? Mongoose Publishing doesn't have a "main book" listed. Closest thing I can find is the one titled "Troubleshooters".
That is "The Main Book". They've split the game into three parts, Troubleshooters is the classic style of low level people running around with wacky hijinks. Theres a Internal Security book, where you play the secret police, and an unreleased High Programmer book, where you take the role of the the "leadership"