There's no denying Schmitt's importance or avoiding his influence.
Schmitt is a renowned, though notorious, jurist and political theorist. His other works include The Concept of the Political, Political Theology, Theory of the Partisan, Dictatorship, and Political Theology.
Schmitt influenced thinkers on the left, like Chantal Mouffe, and those somewhat on the right, like Leo Strauss and Alexander Dugin. This book in particular has been mentioned by Curtis Yarvin (aka Moldbug) as an important text on legitimacy.
And get a closer look at the nature and meaning of constitutional crisis.