How the book's magic affects everything feels like a blur, but there are some things you can distinguish. You seem to be being thrown back hundreds of years and into another country. Your body is ageing a few decades, and you're becoming female. You feel breasts form on your chest and your penis shrink away, as your attraction shifts towards men. Soon you fall into a deep sleep.
*
When you awake, you look around hazily, and take a look at your body. You have enormous breasts, a thick ass, wide childbearing hips and large soft thighs. Slowly you remember the last page you saw- it talked about Queen Henrietta VIII of Britain, and how she had six husbands and severed the country's ties with the Catholic church over her many marriages and separations.
You look over at the man sleeping next to you. This is her first husband, Carlos of Aragon, a Spanish prince who she married after her sister had been with him, and was her husband when she was crowned queen. He gave you two children- Henrietta, who died at a young age, and Martin, who survived to adulthood and became Martin, King of Scots. But Henrietta didn't want sons, she wanted a daughter to be her heir.
Out of curiosity you peek under the blanket. For 48, Carlos has a handsome body. Even so, you recall Henrietta's memories of her lover, Andrew Boleyn, who at present is half her age. Her heart leaps at the thought- such a handsome boy he is with such a big, thick penis! Henrietta felt certain he would give her the daughter she so craved. If only she could separate from Carlos and make him her husband...
At that moment you realize you have a choice. You could continue down the path of history, be Henrietta and have her six husbands, or you could mess with history, try and have another son with Carlos instead of divorcing him.
You wonder what to do...