I am not going to get into a lot of detail about the rules. It is still in early playtest and while the general outline is clear the details are in flux.
First it is in the D&D family of Roleplaying and has elements of both older D&D and the D20 system. But it is not a retro-clone more like Hackmaster Basic, True20, and Castles & Crusades. It is deadlier and more bloody as represented by subsystem involving fumbles, and critical hits.
The spell system is not vancian, although some of the general ideas like spells books are still present. Spells require a roll to see if you get the spell off and what the results are. There is corruption which result from rolling a 1 on a failed spell rolls. High level mages pay a palpable price for their power. You do spellburn which exact a toil on the body but allows you give a needed boost to your spell in a critical moment.
Luck is very important to the DCC RPG and effect everybody differently. Like Spellburn your luck can be used to turn the tide in a critical moment.
Alignment is also important. In the DCC RPG alignment are not just philosophical ideas but represent fundamental factions of the DCC universe. You are not just choosing a belief but who your friends and allies are in the natural and supernatural world. Behind all that are things that man is not meant to know.
Throughout this is the simplicity of original Dungeons & Dragons. Class dominates, and your abilities are 3d6 straight down the line. Some rule subsystems are more complex than OD&D but they are clearly there because these are rules for Swords & Sorcery.
And even at this early stage the writing shines with Joseph Goodman's love of the novels and stories that make up Appendix N of AD&D's Dungeon Master Guide. The playtest adventures I received shine likewise and feel much more like a Moorcock or Howard Adventure than a D&D adventure.
The DCC RPG is going for a specific feel and tone both in it's writing and it's rules. This means that it not going to appeal to all players of the Old School Renaissance. It not D&D but instead is a Swords & Sorcery RPG. But given the what I seen so far I think it going to develop into a game to keep an eye on. That fans of the Dungeon Crawl Classic Modules are going to really like this RPG.