This exact scenario doesn't apply to my practice, but to me, this is a business decision.
There are many providers who offer additional products to their patients (vitamins, lotions, exercise bands, etc.) who charge separately for these products. It's up to your practice whether you think this book is so important, that every patient should have it, regardless of not being paid for it. If patients being given this book saves even 1 phone call from each new mom, then you may decide it's worth it. If you think patients are sticking it in a drawer and not reading it, you may decide to only offer it for sale.