Hubby acting as doula

So my doc asked me at my 6mo apt to think about a doula. I didn't hesitate - I want the most calm, stoic person I know: my husband. If I'm bleeding out and my OB needs a steady hand, he'd be freaking on the inside but all business on the outside. And hell be my best cheerleader.

I explained to him what I was wanting and he's totally game. Not that he'd leave my side, anyway lol but He's ready and willing to be my coach, as well as husband and bestie.

He wants to prep and is thinking of finding a class and reading up .

Does anyone have any suggestions on books or anything that prepared their SO to be their "doula" through labor and delivery?