If you look at the beginning of the forum it has a "why stay" section from MWD, I think she has one of her own articles there which is pretty good...
If that's what you wanted to know...
If you want to know on a psychology level I suggest you read Hold me Tight by Johnson... She explains the dynamics of emotinoal attachment in great detail, as well as how to repair an attachment that's been damaged, abused, and even traumatized by infidelity
