The TFT Companion is a collection of articles, starting with Steve Jackson’s original designer’s notes and errata published in The Space Gamer in 1980. It includes a collection of optional rules, expansions, and adventures created by fans for the magazines of the day, and closes with a collection of the articles posted online as part of the TFT Kickstarter in 2018.
So: 38 years of history of a classic old-school RPG, from birth to . . . well, to rebirth . . . brought together for your enjoyment. Good gaming!