Even though I haven't really gotten into Adventurer, Conqueror, King as much as I'd like to. The Kickstarter for The Sinister Stone of Sakkara
Autarch seems to do a damn good job with the quality of their books. My gut feeling and advice is to get into the ground floor of this one now before ACK's really starts taking off into the higher realms witht their retroclone system.
One thing about Autarch is that they offer a ton of online support for their system and you can learn more about that right over HERE
You can learn more about the Kickstarter right over HERE