"Although little studied today, this Austrian commander fought against Napoleon at the height of his power and came close to defeating him."
This volume is still the standard study of the Austrian Army of the period.
Amazon.com: Napoleon's Great Adversary: 9781885119216: Gunther E. Rothenberg: Books
As this was published in the 90’s there might be thirst for a new biography? See an earlier thread https://www.thenapoleonicwars.net/forum/general-discussions/a-biography-of-archduke-charles
In case it is still the standard study of the Austrian Army of the period (In the anglo phone world I assume) - it is rather a very poor substitude of the numerous German sources about the same subject. The result is alas a distorted picture about the Austrian Army.