I'm so sorry to hear this, and I know it feels like you've been punched in the stomach. I've been there. At least you now know the TRUTH, and can fight for your marriage with the best strategies and tactics.
Michele's book does have a section on "Infidelity," and this by no means your marriage is over or that there's nothing you can do.
You do need to decide how aggressively you want to fight to bust up the affair, versus a more passive, pure-DBing approach. The former worked for me, but it's not for the faint-of-heart.
