The Crawling Chaos
All this changes, however, with the newest (fifth) edition. As part of what can only be described as a renaissance over at Chaosium, the release of the new Masks of Nyarlathotep is a vast improvement over previous editions, and something that you are going to want to risk life, sanity, and hard earned cash to possess. It replaces the original Masks as the definitive edition.
Masks of Nyarlathotep retails at $59.99 US and is worth every single penny. Get it at Chaosium.com or at DriveThruRPG.