Known only through whispers and rumors, the DCC RPG Annual is a legend before its time. Those few who have seen its pages are now but blasted ash. It's your turn, mortal. Be careful when you turn its pages...

From the back of the book:

Spoken about for half a decade in hoary whispers, at long last Goodman Games brings you: the DCC RPG Annual.

You absolutely do not need the DCC Annual to play DCC RPG, nor does any material in the Annual supersede or otherwise change the baseline game experience as expressed in the core rulebook.

There is no rules bloat: only new vistas of imagination.

DCC RPG is a complete role playing game of 1970s Appendix N fantasy.