by Mike Carr
B1 was the first full-length module released by TSR for Basic D&D. It was written by TSR employee and editor Mike Carr, who was a gamer but not primarily of D&D, preferring historical games such as his Fight in the Skies (later Dawn Patrol). This "outsider" approach helped him tailor the module for players unfamiliar with the D&D rules. Thus, B1 contains a number of pages of guidance for new DMs, as well as some additional rules not included in the Holmes rulebook. This format set a precedent for Basic modules; Gygax's B2 also contains several pages of guidance before the module proper.
B1 was also innovative in that the rooms were, for the most part, not stocked with monsters or treasure. This was left for the DM to complete using lists found in the module. A Dragonsfoot thread started by Geoffrey provides many examples of how the dungeon has been stocked by various DMs. This feature was not continued in future Basic modules. The original (orange cover) version of B3 Palace of the Silver Princess did have some rooms of this nature but these were removed when the module was recalled and revised.
Starting in Nov 1978, B1 was packaged with the 2nd edition of the Basic Set, replacing the Monster & Treasure Assortment and Dungeon Geomorphs. The guidance for new DMs was especially useful in this context. B1 was included in the Holmes Set throughout 1979 before being replaced by a new Basic module, B2, at some point in 1980. In 1981, B1 was revised to match the rules of the new Moldvay Basic Set and given a new, brown-bordered cover with full color art by Darlene. See here for a hopefully comprehensive list of changes between the two versions. In Jan 2013, a pdf of revised version was given away for one week as a free pdf by Wizards to mark the beginning of the re-release of the D&D backcatalogue in electronic format.