He has this book on his Kindle.

I find books such as this hilarious.  The stats every year show that women are cheating at a rate rivaling men.  For those of us who have been cuckolded it's a hoot when the myth gets perpetuated that it's only men doing this.  Warning signs for men:

Your SO suddenly (and I mean suddenly) starts dressing like she's going clubbing even when she's leaving for the office;
Your SO suddenly develops a hankering for sexual positions you ain't even heard of;
Your SO's suddenly needs to go help her best female friend with one crisis after another at all hours of the night;
Your SO is packing nothing but sexy dresses and 7-inch heels for that business trip she's about to take;
And my favorite:
You mistakenly get an e-mail meant for the other man.  Gotta love that one.