The book is just an overview rather than original work but the great value is that it is NOT a book about Napoleon so it is not always trying to make a point one way or another.
Bruun, along with more modern authors. I have read (sorry, no ref) is sceptical about the Napoleonic finances. Apart from the domaine extraordinaire problem there is doubt about the reliability of the reported accounts.
The government had a bad record on paying contractors, I believe: the duc de Broglie, who served on the committee of appeal, mentioned more than one case where contractors were forced into bankruptcy by the failure of ministries to pay their side of a contract.

Susan