Hi, lewrail.
I have the Duke and Keilty book. It is a very thorough treatment of the RDC from its design and construction through its years of service on various roads. It is very thorough in its presentation. Although it contains many superb photographs, the book's main attraction is the amount of useful information it presents. I'd have a hard time believing a better RDC book could be produced. I recommend it highly.
I don't own the Crouse book but I've paged through it at meets. I believe it was published by Weekend Chief which is Mr. John Scala's company. His books enjoy an excellent reputation. I own his LIRR diesel book "Diesels of the Sunrise Trail" and, if this book is any indication, the excellent reputation is well deserved. The copies of the Crouse book I've come across have been very expensive - in excess of $100 - so I've held off purchasing a copy.
Again, speaking from experience, the Duke and Keilty book is highly recommended.
Regards,
Bob