May I offer a few more books for your reading list regarding this subject. The first book is about the Invasion of Poland in 1939. It's an Osprey Publication. It's not bad, but there are better books on the subject. (the books I'm suggesting are the ones I've read.). This book goes into some detail regarding the tactics and lessons learned during the beginning of the war. I suggest this book because it shows the "redefinition" of the tactic called "Blitzkrieg".
I think that if you look at the tactics, the Germans could very well be called the inventors of Modern Warefare. But I think there is room for a discussion there. There were also Americans who were also highly skilled tacticians. For example, General Patton.
So is the discussion truly about tactics and the use of this new type of warefare called "Blitzkrieg" or could we be talking about the morale and the lack of qualified leaders at the beginning of 1940 for the allies. You can also add to that list the political atmosphere in 1939-1940. Between the German-Soviet pact and their combined invasion of Poland, I would tend to believe that France or any other nation, would feel the cause was lost with two formidable enemies preparing for war against them.
Book link:
http://www.ospreypublishing.com/store/Poland-1939_9781841764085/Two other books I would also suggest regarding the "Battle of France", but from a different perspective. (isn't that what history is all about....perspectives.) The first book is called "The Lost Hopes-Polish Fighters over France 1940".
http://www.akpro.elk.com.pl/losthopes/index.phpThis book discusses the problems that France and it's allies faced in 1940. It details the problems with the lack of leaders and several allied units not wanting to be under French control. It also gives a brief glimpse into the morale of the French and insurmountable odds the allies faced in 1940. This book can be difficult to find. The link is from the publisher. Don't worry, it's in English (and Polish).
The second book is from the MMP Series called "GC 1/145 in France 1940". Again, this book looks more into the history of one squadron that took part in the Battle of France. I offer it only as some additional insight into what truly happened to France in 1940. Just another warning though, finding this book might be difficult. It's sold out.
http://mmpbooks.biz/mmp/books.php?book_id=80I would also like to add that my interest in the Battle of France became the focus of my family history. In the two books I listed about the Polish Air Force in France, my Grandfather's cousin is mentioned. (The second book has his photo). He was killed flying a C-714 Caudron on June 10, 1940 during the Battle of France.
I hope that you were able to bear with my rambling and that you find these book suggestions to your enjoyment.