ACKS is pretty easy to leverage for other games. The intent is for most-everything to remain compatible. I may or may not publish new editions of some of the books, depending on how well ACKS II does.

I would say if you wanted to have the maximum material to exploit, without overlapping with material in ACKS II, you should purchase BY THIS AXE, HEROIC FANTASY HANDBOOK, BARBARIAN CONQUERORS, ALMANAC OF UNUSUAL MAGIC, and the various AX series of adventures. The best material from Axioms Compenium #1 is already incorporated into ACKS II, but there is lots of value in Axioms Compendium #2. If you want to do tabletop mass combat with figures or stands, get DOMAINS AT WAR: BATTLES and TROOPS AND TERRAIN.

Thanks for the kind words and support!