Big Red Book

A term originating with players of Warhammer Fantasy, the term "Big Red Book" (or BRB) refers to the core rulebook. Although the term began in the 6th edition when, rather than a small booklet containing the rules, large hardcover books were sold, it is also applied to the core books of past editions as well despite not being big or red (rather, resembling the Army Books of today). The books were sold separate from starter sets in a hardcover form which contained glossy full color images of models in different scenes and paint jobs from 'Eavy Metal, and a large section dedicated to the lore of the game. The inclusion of this glorified (if glorious) catalog put the price tag for each editions core rules at $60+.

Despite this, small booklets containing the exact same rules portion and a small amount of lore were packaged with the starter sets of each edition (usually not much more expensive than the BRB) which lead to players looking to update to the practice of buying a starter set, and selling the miniatures they didn't want online (making it very easy for people looking to start an army for one of the armies in that edition starter box to get a beginning force cheap and fast).

The practice was applied to Warhammer 40,000 as well, and much like how some Fantasy players mistakenly call Army Books "Codexes", some 40k players call the hardcover rules the Big Red (or Black) Book. 7th edition 40k split the Big Black Book into a set of three books.

In 6th Edition however, Games Workshop changed their format; the Big Black Book (now white and red) contained no fluff, but instead was the rules covering the crunch of all of the armies in the game with a guide for new players to choose their first (or additional ones) on preference of playstyle. Fluff books are now sold separately in lieu of Codexes. Reaction was predictably mixed, some praising it for requiring only one book to play rather than $60 for core and $50 for each army, others readying their torches.

Warhammer Fantasy also received a format change at the end of 8th Edition, during the End Times event. Each book (the first at $80, second at $60) was FAQ'd into the Big Red Book, changing some rules, adding two armies (made of existing armies combined) to the game, and increasing the number of characters that can be fielded. Rumors swirl that 9e will contain a similar Big Red(?) Book as 40k, while 40k will receive event books changing the core rules.