Complex sentence: The original "Dungeons & Dragons" boxed set by Gary Gygax and Dave Arneson was published by TSR, Inc. in 1974, and initially comprised the original edition of the Dungeons & Dragons fantasy role-playing game.
Split into simpler sentences: The original "Dungeons & Dragons" (commonly abbreviated "D&D") boxed set by Gary Gygax and Dave Arneson was published by TSR, Inc. in 1974. It initially included the original edition of the Dungeons & Dragons fantasy role-playing game.