I do believe there are subtle differences between how men and women react to uncovering infidelity. Am I missing something?
No, you're not missing anything, but it really is subtle enough not to matter all that much. I remember thinking the same thing following D-day, but after reading a number of infidelity books, and years on SI, the betrayed spouses (BS) reactions to an affair tend to be similar between men and women. In other words, it's all over the map. You just can't predict how someone will react to betrayal. One thing for sure, there is almost always a lot of mental pain and suffering, followed by an emotional rollercoaster that can last for months, or longer.
IMO, far and away the best book on the topic of infidelity and betrayal is Not "Just Friends" by Shirley Glass. This book is not gender specific. It will provide you much insight into the psychology of affairs, how they get started and why they happen. This book will also help you understand the emotional suffering you are going through, as well as many other things you will need to understand. I can't recommend this book enough.
If you're looking to improve your relationship, I recommend the book, Secrets of Happily Married Men by Scott Haltzman.
As far as websites, as others have pointed out, there is a "Betrayed Men" sub-forum in the I Can Relate section of SI.
Also, if the suffering becomes overwhelming and you're looking for immediate help or answers, don't overlook the possibility of individual counseling (IC). Following D-day, I found a good counselor that knew how to handle infidelity. I only went a few sessions, but the IC's help was invaluable to me at the time.