Single dad with a teenage daughter

My niece is 11 and has been asking questions about puberty and her body a lot recently, which I am completely fine with answering. I let my brother know that we were having these conversations, just a heads up, and he admits he has no idea either. He's never lived with a woman long term, his baby mama isnt in the picture, and his bio mom is far from helpful. So although I'm happy to answer whatever questions my niece has for me, what are some good books, or sources for him to help understand what shes going through?