This book reminded me very much of 'Redcoat' by Richard Holmes and 'The Art of War in the Age of Marlborough' by David Chandler. In contrast to these books 'Military experience in the age of reason' is not limited to the British army (as 'Redcoat' is) and focuses on a later period (say from the War of Polish Succession to the American War, focusing heavily on the 7 Years' War and the War of Austrian Succession) than 'Art of War'.
Rather than treating any war or campaign as such, the book is organized topically around 'topics' such as the officer class, the common soldier, the campaign, the battle, etc. The book is underpinned by Duffy's extensive knowledge of warfare of this period and contains 100s of quotes from contemporary sources. Duffy clearly loves his topic and it shows.
What I found most interesting was the description of the officer class; obsessed with 'honor', ridden with gambling debts, perpetually drunk and prone to dueling. In general, I think Duffy did a great job in giving the reader a good feel of 18th century warfare. Personally I find this type of book (topically structured) somewhat less readible than chronologically structured descriptions of wars / campaigns / battles, but to each his own.