Help with book title, please?

There's a woman, whose name I also can't remember, who writes books about how the body works.

One was about the gut, one is about sex, and there are others I can't remember.

I think she also wrote a book about space or space travel.

Any idea about the name of the gut book, or the author's name?

Her books always make the NYT best-seller list.

I'm hoping my crappy memory tonight has to do with meds I got for a procedure at the hospital today. Otherwise, I'm really slipping!

Thanks if you can help.