Hans-Hermann Hoppe was a very close associate of Murray Rothbards, and notably they get bunched in together very often due to the drastic overlap of the two. I recommend checking out Anatomy of The State, What has Government Done to Our Money, From Aristocracy to Monarchy to Democracy, Democracy: The God That Failed, and Getting Libertarianism Right. The Latter Three are by Hoppe, The Former Two are by Murray Rothbard.