HA is considered one of the most important works in the Austrian tradition. Going back to the foundation of the school, there is "Principles of Economics" by Carl Menger. Going even further back before the school, you have Adam Smith's "The Wealth of Nations" which is a timeless classic. Moving forward, you might want to look at "Choice in Currency: A Way to Stop Inflation" by Friedrich A. von Hayek. For shorter more digestible works: "The Austrian Theory of the Trade Cycle and Other Essays" edited by Richard Ebeling.

Keynesians have brought us so far away from the principles of sound money that there is no modern context. We are neck deep in the Zimbabwe School of Economics.